active tectonic features: Topics by Science.gov

Sample records for active tectonic features

A global tectonic activity map with orbital photographic supplement

NASA Technical Reports Server (NTRS)

Lowman, P. D., Jr.

1981-01-01

A three part map showing equatorial and polar regions was compiled showing tectonic and volcanic activity of the past one million years, including the present. Features shown include actively spreading ridges, spreading rates, major active faults, subduction zones, well defined plates, and volcanic areas active within the past one million years. Activity within this period was inferred from seismicity (instrumental and historic), physiography, and published literature. The tectonic activity map was used for planning global geodetic programs of satellite laser ranging and very long base line interferometry and for geologic education.
Analysis of tectonic features in US southwest from Skylab photographs

NASA Technical Reports Server (NTRS)

Abdel-Gawad, M. (Principal Investigator); Tubbesing, L.

1975-01-01

The author has identified the following significant results. Skylab photographs were utilized to study faults and tectonic lines in selected areas of the U.S. Southwest. Emphasis was on elements of the Texas Zone in the Mojave Desert and the tectonic intersection in southern Nevada. Transverse faults believed to represent the continuation of the Texas Zone were found to be anomalous in strike. This suggests that the Mojave Desert block was rotated counterclockwise as a unit with the Sierra Nevada. Left-lateral strike-slip faults in Lake Mead area are interpreted as elements of the Wasatch tectonic zone; their anomalous trend indicates that the Lake Mead area has rotated clockwise with the Colorado Plateau. A tectonic model relating major fault zones to fragmentation and rotation of crustal blocks was developed. Detailed correlation of the high resolution S190B metric camera photographs with U-2 photographs and geologic maps demonstrates the feasibility of utilizing S190B photographs for the identification of geomorphic features associated with recent and active faults and for the assessment of seismic hazards.
Studies in geophysics: Active tectonics

NASA Technical Reports Server (NTRS)

1986-01-01

Active tectonics is defined within the study as tectonic movements that are expected to occur within a future time span of concern to society. Such movements and their associated hazards include earthquakes, volcanic eruptions, and land subsidence and emergence. The entire range of geology, geophysics, and geodesy is, to some extent, pertinent to this topic. The needs for useful forecasts of tectonic activity, so that actions may be taken to mitigate hazards, call for special attention to ongoing tectonic activity. Further progress in understanding active tectonics depends on continued research. Particularly important is improvement in the accuracy of dating techniques for recent geologic materials.
A Digital Tectonic Activity Map of the Earth

NASA Technical Reports Server (NTRS)

Lowman, Paul; Masuoka, Penny; Montgomery, Brian; OLeary, Jay; Salisbury, Demetra; Yates, Jacob

1999-01-01

The subject of neotectonics, covering the structures and structural activity of the last 5 million years (i.e., post-Miocene) is a well-recognized field, including "active tectonics," focussed on the last 500,000 years in a 1986 National Research Council report of that title. However, there is a cartographic gap between tectonic maps, generally showing all features regardless of age, and maps of current seismic or volcanic activity. We have compiled a map intended to bridge this gap, using modern data bases and computer-aided cartographic techniques. The maps presented here are conceptually descended from an earlier map showing tectonic and volcanic activity of the last one million years. Drawn by hand with the National Geographic Society's 1975 "The Physical World" map as a base, the 1981 map in various revisions has been widely reproduced in textbooks and various technical publications. However, two decades of progress call for a completely new map that can take advantage of new knowledge and cartographic techniques. The digital tectonic activity map (DTM), presented in shaded relief (Fig. 1) and schematic (Fig. 2) versions, is the result. The DTM is intended to show tectonism and volcanism of the last one million years, a period long enough to be representative of global activity, but short enough that features such as fault scarps and volcanos are still geomorphically recognizable. Data Sources and Cartographic Methods The DTM is based on a wide range of sources, summarized in Table 1. The most important is the digital elevation model, used to construct a shaded relief map. The bathymetry is largely from satellite altimetry, specifically the marine gravity compilations by Smith and Sandwell (1996). The shaded relief map was designed to match the new National Geographic Society world physical map (1992), although drawn independently, from the digital elevation model. The Robinson Projection is used instead of the earlier Van der Grinten one. Although neither
Active tectonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1986-01-01

This study is part of a series of Studies in Geophysics that have been undertaken for the Geophysics Research Forum by the Geophysics Study Committee. One purpose of each study is to provide assessments from the scientific community to aid policymakers in decisions on societal problems that involve geophysics. An important part of such assessments is an evaluation of the adequacy of current geophysical knowledge and the appropriateness of current research programs as a source of information required for those decisions. The study addresses our current scientific understanding of active tectonics --- particularly the patterns and rates of ongoing tectonicmore » processes. Many of these processes cannot be described reasonably using the limited instrumental or historical records; however, most can be described adequately for practical purposes using the geologic record of the past 500,000 years. A program of fundamental research focusing especially on Quaternary tectonic geology and geomorphology, paleoseismology, neotectonics, and geodesy is recommended to better understand ongoing, active tectonic processes. This volume contains 16 papers. Individual papers are indexed separately on the Energy Database.« less
Significant Centers of Tectonic Activity as Identified by Wrinkle Ridges for the Western Hemisphere of Mars

NASA Technical Reports Server (NTRS)

Anderson, R.C.; Haldemann, A. F. C.; Golombek, M. P.; Franklin, B. J.; Dohm, J. M.; Lias, J.

2000-01-01

The western hemisphere region of Mars has been the site of numerous scientific investigations regarding its tectonic evolution. For this region of Mars, the dominant tectonic region is the Tharsis province. Tharsis is characterized by an enormous system of radiating grabens and a circumferential system of wrinkle ridges. Past investigations of grabens associated with Tharsis have identified specific centers of tectonic activity. A recent structural analysis of the western hemisphere region of Mars which includes the Tharsis region, utilized 25,000 structures to determine the history of local and regional centers of tectonic activity based primarily on the spatial and temporal relationships of extensional features. This investigation revealed that Tharsis is more structurally complex (heterogeneous) than has been previously identified: it consists of numerous regional and local centers of tectonic activity (some are more dominant and/or more long lived than others). Here we use the same approach as Anderson et al. to determine whether the centers of tectonic activity that formed the extensional features also contributed to wrinkle ridge (compressional) formation.
Complex Plate Tectonic Features on Planetary Bodies: Analogs from Earth

NASA Astrophysics Data System (ADS)

Stock, J. M.; Smrekar, S. E.

2016-12-01

We review the types and scales of observations needed on other rocky planetary bodies (e.g., Mars, Venus, exoplanets) to evaluate evidence of present or past plate motions. Earth's plate boundaries were initially simplified into three basic types (ridges, trenches, and transform faults). Previous studies examined the Moon, Mars, Venus, Mercury and icy moons such as Europa, for evidence of features, including linear rifts, arcuate convergent zones, strike-slip faults, and distributed deformation (rifting or folding). Yet, several aspects merit further consideration. 1) Is the feature active or fossil? Earth's active mid ocean ridges are bathymetric highs, and seafloor depth increases on either side; whereas, fossil mid ocean ridges may be as deep as the surrounding abyssal plain with no major rift valley, although with a minor gravity low (e.g., Osbourn Trough, W. Pacific Ocean). Fossil trenches have less topographic relief than active trenches (e.g., the fossil trench along the Patton Escarpment, west of California). 2) On Earth, fault patterns of spreading centers depend on volcanism. Excess volcanism reduced faulting. Fault visibility increases as spreading rates slow, or as magmatism decreases, producing high-angle normal faults parallel to the spreading center. At magma-poor spreading centers, high resolution bathymetry shows low angle detachment faults with large scale mullions and striations parallel to plate motion (e.g., Mid Atlantic Ridge, Southwest Indian Ridge). 3) Sedimentation on Earth masks features that might be visible on a non-erosional planet. Subduction zones on Earth in areas of low sedimentation have clear trench -parallel faults causing flexural deformation of the downgoing plate; in highly sedimented subduction zones, no such faults can be seen, and there may be no bathymetric trench at all. 4) Areas of Earth with broad upwelling, such as the North Fiji Basin, have complex plate tectonic patterns with many individual but poorly linked ridge
Puzzling features of western Mediterranean tectonics explained by slab dragging

NASA Astrophysics Data System (ADS)

Spakman, Wim; Chertova, Maria V.; van den Berg, Arie.; van Hinsbergen, Douwe J. J.

2018-03-01

The recent tectonic evolution of the western Mediterranean region is enigmatic. The causes for the closure of the Moroccan marine gateway prior to the Messinian salinity crisis, for the ongoing shortening of the Moroccan Rif and for the origin of the seismogenic Trans-Alboran shear zone and eastern Betics extension are unclear. These puzzling tectonic features cannot be fully explained by subduction of the east-dipping Gibraltar slab in the context of the regional relative plate motion frame. Here we use a combination of geological and geodetic data, as well as three-dimensional numerical modelling of subduction, to show that these unusual tectonic features could be the consequence of slab dragging—the north to north-eastward dragging of the Gibraltar slab by the absolute motion of the African Plate. Comparison of our model results to patterns of deformation in the western Mediterranean constrained by geological and geodetic data confirm that slab dragging provides a plausible mechanism for the observed deformation. Our results imply that the impact of absolute plate motion on subduction is identifiable from crustal observations. Identifying such signatures elsewhere may improve the mantle reference frame and provide insights on subduction evolution and associated crustal deformation.
Hydrothermal and tectonic activity in northern Yellowstone Lake, Wyoming

USGS Publications Warehouse

Johnson, S.Y.; Stephenson, W.J.; Morgan, L.A.; Shanks, Wayne C.; Pierce, K.L.

2003-01-01

Yellowstone National Park is the site of one of the world's largest calderas. The abundance of geothermal and tectonic activity in and around the caldera, including historic uplift and subsidence, makes it necessary to understand active geologic processes and their associated hazards. To that end, we here use an extensive grid of high-resolution seismic reflection profiles (???450 km) to document hydrothermal and tectonic features and deposits in northern Yellowstone Lake. Sublacustrine geothermal features in northern Yellowstone Lake include two of the largest known hydrothermal explosion craters, Mary Bay and Elliott's. Mary Bay explosion breccia is distributed uniformly around the crater, whereas Elliott's crater breccia has an asymmetric distribution and forms a distinctive, ???2-km-long, hummocky lobe on the lake floor. Hydrothermal vents and low-relief domes are abundant on the lake floor; their greatest abundance is in and near explosion craters and along linear fissures. Domed areas on the lake floor that are relatively unbreached (by vents) are considered the most likely sites of future large hydrothermal explosions. Four submerged shoreline terraces along the margins of northern Yellowstone Lake add to the Holocene record or postglacial lake-level fluctuations attributed to "heavy breathing" of the Yellowstone magma reservoir and associated geothermal system. The Lake Hotel fault cuts through northwestern Yellowstone Lake and represents part of a 25-km-long distributed extensional deformation zone. Three postglacial ruptures indicate a slip rate of ???0.27 to 0.34 mm/yr. The largest (3.0 m slip) and most recent event occurred in the past ???2100 yr. Although high heat flow in the crust limits the rupture area of this fault zone, future earthquakes of magnitude ???5.3 to 6.5 are possible. Earthquakes and hydrothermal explosions have probably triggered landslides, common features around the lake margins. Few high-resolution seismic reflection surveys have
Late Tharsis tectonic activity and implications for Early Mars

NASA Astrophysics Data System (ADS)

Bouley, S.; Baratoux, D.; Paulien, N.; Missenard, Y.; Saint-Bezar, B.

2017-12-01

Constraining the timing of Tharsis volcanism is critical to understanding the planet's evolution including its climate, surface environment and mantle dynamics. The tectonic history of the Tharsis bulge was previously documented from the distribution and ages of related tectonic features [1]. Here we revisit the ages of 7493 Tharsis-related tectonic features based on their relationship with stratigraphic units defined in the new geological map [2]. Conversely to previous tectonic mapping [1], which suggested that Tharsis growth was nearly achieved during the Noachian, we find a protracted growth of Tharsis during the Hesperian. Faulting at Tempe Terra, Claritas and Coracis Fossae and Thaumasia Planum confirms that tectonic deformation started during the Noachian. Accumulated tectonic deformation was maximum in the Early Hesperian for compressional strain (Solis, Lunae and Ascuris Planum) and extended over time from Noachian to Amazonian for extensional strain (Noctis Labyrinthus and Fossae, Sinai Planum and Tractus, Ulysses and Fortuna fossae, Alba Patera). This new scenario is consistent with a protracted growth of Tharsis dome during the Hesperian and with the timing a large Tharsis-driven true polar wander post-dating the incision of Late Noachian/Hesperian valley networks[3]. References:[1] Anderson et al. JGR-Planets 106, E9, 20,563-20,585 (2001).[2] Tanaka, K.L. et al. Geologic map of Mars (2014). [3] Bouley et al. Nature doi:10.1038 (2016)
Recent tectonic activity on Pluto driven by phase changes in the ice shell

NASA Astrophysics Data System (ADS)

Hammond, Noah P.; Barr, Amy C.; Parmentier, Edgar M.

2016-07-01

The New Horizons spacecraft has found evidence for geologic activity on the surface of Pluto, including extensional tectonic deformation of its water ice bedrock see Moore et al. (2016). One mechanism that could drive extensional tectonic activity is global surface expansion due to the partial freezing of an ocean. We use updated physical properties for Pluto and simulate its thermal evolution to understand the survival of a possible subsurface ocean. For thermal conductivities of rock less than 3 W m-1 K-1, an ocean forms and at least partially freezes, leading to recent extensional stresses in the ice shell. In scenarios where the ocean freezes and the ice shell is thicker than 260 km, ice II forms and causes global volume contraction. Since there is no evidence for recent compressional tectonic features, we argue that ice II has not formed and that Pluto's ocean has likely survived to present day.
Understanding the Tectonic Features in the South China Sea By Analyzing Magnetic Anomalies

NASA Astrophysics Data System (ADS)

Guo, L.; Meng, X.; Shi, L.; Yao, C.

2011-12-01

The South China Sea (SCS) is surrounded by the Eurasia, Pacific and India-Australia plates. It formed during Late Oligocene-Early Miocene, and is one of the largest marginal seas in the Western Pacific. The collision of Indian subcontinent and Eurasian plate in the northwest, back-arc spreading in the centre and subduction beneath the Philippine plate along Manila trench in the east and along Palawan trough in the south had produced the complex tectonic features in the SCS that we can see today. In the past few decades, a variety of geophysical methods were conducted to study geological tectonics and evolution of the SCS. Here, we analyzed the magnetic data of this area using new data enhancement techniques to understand the regional tectonic features. We assembled the magnetic anomalies data with a resolution of two arc-minute from the World Digital Magnetic Anomaly Map, and then gridded the data on a regular grid. Then we used the method of reduction to the pole at low latitude with varying magnetic inclinations to stably reduce the magnetic anomalies. Then we used the preferential continuation method based on Wiener filtering and Green's equivalence principle to separate the reduced-to-pole (RTP) magnetic anomalies, and subsequently analyze the regional and residual anomalies. We also calculated the directional horizontal derivatives and the tilt-angle derivative of the data to derive clearer geological structures with more details. Then we calculated the depth of the magnetic basement surface in the area by 3D interface inversion. From the results of the preliminary processing, we analyzed the main faults, geological structures, magma distribution and tectonic features in the SCS. In the future, the integrated interpretation of the RTP magnetic anomalies, Bouguer gravity anomalies and other geophysical methods will be performed for better understanding the deep structure , the tectonic features and evolution of the South China Sea. Acknowledgment: We
Tectonics of Europa

NASA Astrophysics Data System (ADS)

Kattenhorn, S. A.; Hurford, T. A.

2007-12-01

This review of Europan tectonics previews a chapter of the forthcoming text "Europa". After the Voyager flyby of the icy moon Europa in 1979, models were developed that attributed pervasive surface fracturing to the effects of tidal forcing due to the gravitational pull of Jupiter. The late 1990s Galileo mission returned high resolution coverage of the surface, allowing a diverse range of tectonic features to be identified. Subsequent description, interpretation, and modeling of these features has resulted in significant developments in five key themes: (1) What drives the tectonics? (2) What are the formation mechanisms of the various types of tectonic features? (3) What are the implications for a subsurface ocean? (4) What is the nature and thickness of the ice shell? (5) Is Europa currently tectonically active? We highlight key developments pertaining to these fundamental issues, focusing on the following elements: (1) Many fracture patterns can be correlated with theoretical stress fields induced by diurnal tidal forcing and long-term effects of nonsynchronous rotation of the ice shell; however, these driving mechanisms alone cannot explain all fracturing. The tectonic fabric has likely been affected by additional contributing effects: tidal despinning, orbital evolution, interior differentiation, polar wander, finite obliquity, stresses due to shell thickening, endogenic forcing by convection and diapirism, and secondary effects driven by strike-slip faulting and plate flexure. (2) Due to the prevalence of global tension, a low lithostatic gradient, and the inherent weakness of ice, tectonic features likely have predominantly extensional primary formation mechanisms (e.g. surface fractures, ridges, and normal faults). There has been no categorical documentation of fracture development by compressive shearing. Even so, the constantly changing nature of the tidal stress field results in shearing reactivation of cracks being important for the morphologic and
MEVTV Workshop on Tectonic Features on Mars

NASA Technical Reports Server (NTRS)

Watters, Thomas R. (Editor); Golombek, Matthew P. (Editor)

1989-01-01

The state of knowledge of tectonic features on Mars was determined and kinematic and mechanical models were assessed for their origin. Three sessions were held: wrinkle ridges and compressional structure; strike-slip faults; and extensional structures. Each session began with an overview of the features under discussion. In the case of wrinkle ridges and extensional structures, the overview was followed by keynote addresses by specialists working on similar structures on the Earth. The first session of the workshop focused on the controversy over the relative importance of folding, faulting, and intrusive volcanism in the origin of wrinkle ridges. The session ended with discussions of the origin of compressional flank structures associated with Martian volcanoes and the relationship between the volcanic complexes and the inferred regional stress field. The second day of the workshop began with the presentation and discussion of evidence for strike-slip faults on Mars at various scales. In the last session, the discussion of extensional structures ranged from the origin of grabens, tension cracks, and pit-crater chains to the origin of Valles Marineris canyons. Shear and tensile modes of brittle failure in the formation of extensional features and the role of these failure modes in the formation of pit-crater chains and the canyons of Valles Marineris were debated. The relationship of extensional features to other surface processes, such as carbonate dissolution (karst) were also discussed.
Tectonism

NASA Image and Video Library

2011-10-24

This image from NASA 2001 Mars Odyssey spacecraft shows evidence of tectonic stresses that deform and fracture rocks and planetary surfaces. Right angles seen here are a good indication that the feature was formed by tectonic stresses.
Active tectonics and earthquake potential of the Myanmar region

NASA Astrophysics Data System (ADS)

Wang, Yu; Sieh, Kerry; Tun, Soe Thura; Lai, Kuang-Yin; Myint, Than

2014-04-01

This paper describes geomorphologic evidence for the principal neotectonic features of Myanmar and its immediate surroundings. We combine this evidence with published structural, geodetic, and seismic data to present an overview of the active tectonic architecture of the region and its seismic potential. Three tectonic systems accommodate oblique collision of the Indian plate with Southeast Asia and extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Subduction and collision associated with the Sunda megathrust beneath and within the Indoburman range and Naga Hills accommodate most of the shortening across the transpressional plate boundary. The Sagaing fault system is the predominant locus of dextral motion associated with the northward translation of India. Left-lateral faults of the northern Shan Plateau, northern Laos, Thailand, and southern China facilitate extrusion of rocks around the eastern syntaxis of the Himalaya. All of these systems have produced major earthquakes within recorded history and continue to present major seismic hazards in the region.
Data for Quaternary faults, liquefaction features, and possible tectonic features in the Central and Eastern United States, east of the Rocky Mountain Front

USGS Publications Warehouse

Crone, Anthony J.; Wheeler, Russell L.

2000-01-01

The USGS is currently leading an effort to compile published geological information on Quaternary faults, folds, and earthquake-induced liquefaction in order to develop an internally consistent database on the locations, ages, and activity rates of major earthquake-related features throughout the United States. This report is the compilation for such features in the Central and Eastern United States (CEUS), which for the purposes of the compilation, is defined as the region extending from the Rocky Mountain Front eastward to the Atlantic seaboard. A key objective of this national compilation is to provide a comprehensive database of Quaternary features that might generate strong ground motion and therefore, should be considered in assessing the seismic hazard throughout the country. In addition to printed versions of regional and individual state compilations, the database will be available on the World-Wide Web, where it will be readily available to everyone. The primary purpose of these compilations and the derivative database is to provide a comprehensive, uniform source of geological information that can by used to complement the other types of data that are used in seismic-hazard assessments. Within our CEUS study area, which encompasses more than 60 percent of the continuous U.S., we summarize the geological information on 69 features that are categorized into four classes (Class A, B, C, and D) based on what is known about the feature's Quaternary activity. The CEUS contains only 13 features of tectonic origin for which there is convincing evidence of Quaternary activity (Class A features). Of the remaining 56 features, 11 require further study in order to confidently define their potential as possible sources of earthquake-induced ground motion (Class B), whereas the remaining features either lack convincing geologic evidence of Quaternary tectonic faulting or have been studied carefully enough to determine that they do not pose a significant seismic hazard
Geomorphology, tectonics, and exploration

NASA Technical Reports Server (NTRS)

Sabins, F. F., Jr.

1985-01-01

Explorationists interpret satellite images for tectonic features and patterns that may be clues to mineral and energy deposits. The tectonic features of interest range in scale from regional (sedimentary basins, fold belts) to local (faults, fractures) and are generally expressed as geomorphic features in remote sensing images. Explorationists typically employ classic concepts of geomorphology and landform analysis for their interpretations, which leads to the question - Are there new and evolving concepts in geomorphology that may be applicable to tectonic analyses of images?
Topographic representation using DEMs and its applications to active tectonics research

NASA Astrophysics Data System (ADS)

Oguchi, T.; Lin, Z.; Hayakawa, Y. S.

2016-12-01

Identifying topographic deformations due to active tectonics has been a principal issue in tectonic geomorphology. It provides useful information such as whether a fault has been active during the recent past. Traditionally, field observations, conventional surveying, and visual interpretation of topographic maps, aerial photos, and satellite images were the main methods for such geomorphological investigations. However, recent studies have been utilizing digital elevation models (DEMs) to visualize and quantitatively analyze landforms. There are many advantages to the use of DEMs for research in active tectonics. For example, unlike aerial photos and satellite images, DEMs show ground conditions without vegetation and man-made objects such as buildings, permitting direct representation of tectonically deformed landforms. Recent developments and advances in airborne LiDAR also allow the fast creation of DEMs even in vegetated areas such as forested lands. In addition, DEMs enable flexible topographic visualization based on various digital cartographic and computer-graphic techniques, facilitating identification of particular landforms such as active faults. Further, recent progress in morphometric analyses using DEMs can be employed to quantitatively represent topographic characteristics, and objectively evaluate tectonic deformation and the properties of related landforms. This paper presents a review of DEM applications in tectonic geomorphology, with attention to historical development, recent advances, and future perspectives. Examples are taken mainly from Japan, a typical tectonically active country. The broader contributions of DEM-based active tectonics research to other fields, such as fluvial geomorphology and geochronology, will also be discussed.
Plate Tectonics: A Framework for Understanding Our Living Planet.

ERIC Educational Resources Information Center

Achache, Jose

1987-01-01

Discusses some of the events leading to the development of the theory of plate tectonics. Describes how seismic, volcanic, and tectonic features observed at the surface of the planet are now seen as a consequence of intense internal activity, and makes suggestions about their further investigation. (TW)

Incorporation of New and Old Tectonics Concepts Into a Modern Course in Tectonics.

ERIC Educational Resources Information Center

Hatcher, Robert D., Jr.

1983-01-01

Describes a graduate-level tectonics course which includes the historical basis for modern tectonics concepts and an in-depth review of pros/cons of plate tectonics. Tectonic features discussed include: ocean basins; volcanic arcs; continental margins; continents; orogenic belts; foreland fold and thrust belts; volcanic/plutonic belts of orogens;…
Off-axis volcano-tectonic activity during continental rifting: Insights from the transversal Goba-Bonga lineament, Main Ethiopian Rift (East Africa)

NASA Astrophysics Data System (ADS)

Corti, Giacomo; Sani, Federico; Agostini, Samuele; Philippon, Melody; Sokoutis, Dimitrios; Willingshofer, Ernst

2018-03-01

The Main Ethiopian Rift, East Africa, is characterized by the presence of major, enigmatic structures which strike approximately orthogonal to the trend of the rift valley. These structures are marked by important deformation and magmatic activity in an off-axis position in the plateaus surrounding the rift. In this study, we present new structural data based on a remote and field analysis, complemented with analogue modelling experiments, and new geochemical analysis of volcanic rocks sampled in different portions of one of these transversal structures: the Goba-Bonga volcano-tectonic lineament (GBVL). This integrated analysis shows that the GBVL is associated with roughly E-W-trending prominent volcano-tectonic activity affecting the western plateau. Within the rift floor, the approximately E-W alignment of Awasa and Corbetti calderas likely represent expressions of the GBVL. Conversely, no tectonic or volcanic features of similar (E-W) orientation have been recognized on the eastern plateau. Analogue modelling suggests that the volcano-tectonic features of the GBVL have probably been controlled by the presence of a roughly E-W striking pre-existing discontinuity beneath the western plateau, which did not extend beneath the eastern plateau. Geochemical analysis supports this interpretation and indicates that, although magmas have the same sub-lithospheric mantle source, limited differences in magma evolution displayed by products found along the GBVL may be ascribed to the different tectonic framework to the west, to the east, and in the axial zone of the rift. These results support the importance of the heterogeneous nature of the lithosphere and the spatial variations of its structure in controlling the architecture of continental rifts and the distribution of the related volcano-tectonic activity.
Geodynamic features along the Christianna-Santorini-Kolumbo tectonic line (South Aegean Sea, Greece)

NASA Astrophysics Data System (ADS)

Nomikou, Paraskevi; Papanikolaou, Dimitrios; Carey, Steve; Bejelou, Konstantina; Sakellariou, Dimitris; Kilias, Stefanos; Camilli, Rich; Escartin, Javier; Bell, Kathrine; Parks, Michelle

2013-04-01

Numerous oceanographic surveys have been conducted in Santorini Volcanic Group (South Aegean Sea) since 2001, revealing the spectacular morphology of the seafloor (multibeam data) and the sub-seafloor stratigraphic horizons (seismic profiles). Technological advancements in seafloor exploration such as ROVs and a submersible, enabled us to observe products of submarine volcanism that were previously inaccessible. In addition, gravity and box coring, geological and biological samples have been collected from selected areas for further analysis. The offshore geophysical survey in Santorini shows that recent volcanism occurred along a NE-SW tectonic zone named as Christianna-Santorini-Kolumbo (CSK) line. Christiana islets and three newly discovered submarine volcanic domes, with small colonies of yellow, presumably sulfur-reducing hydrothermal bacteria, occur in the southwestern part of the line. The presently active intra caldera volcanic domes of Palea and Nea Kameni islands and the low temperature (17-24°C) vent mounds covered by yellowish bacterial mat occupy the middle part of the line. The Santorini vent field is linked with the Kolumbo normal fault onshore which is likely controlling the pathways of hydrothermal circulation within the caldera. The most prominent feature at the NE part of this zone, is Kolumbo submarine volcanic chain which is extended 20Km with several volcanic domes aligned along this direction. The Kolumbo volcano had an explosive eruption in 1650 that killed 70 people on Santorini. The hydrothermal vent field in the crater floor of Kolumbo consists dominantly of active and inactive sulfide-sulfate structures in the form of vertical spires and pinnacles, mounds and flanges along a NE-SW trend, with temperatures up to 220°C and vigorous CO2 gas emission. For several years, the highest frequency of earthquakes was concentrated mainly in the vicinity of Kolumbo volcano. However, during 2011-2012 both seismic and geodetic unrest began abruptly
Tectonic activity evolution of the Scotia-Antarctic Plate boundary from mass transport deposit analysis

NASA Astrophysics Data System (ADS)

Pérez, Lara F.; Bohoyo, Fernando; Hernández-Molina, F. Javier; Casas, David; Galindo-Zaldívar, Jesús; Ruano, Patricia; Maldonado, Andrés.

2016-04-01

The spatial distribution and temporal occurrence of mass transport deposits (MTDs) in the sedimentary infill of basins and submerged banks near the Scotia-Antarctic plate boundary allowed us to decode the evolution of the tectonic activity of the relevant structures in the region from the Oligocene to present day. The 1020 MTDs identified in the available data set of multichannel seismic reflection profiles in the region are subdivided according to the geographic and chronological distributions of these features. Their spatial distribution reveals a preferential location along the eastern margins of the eastern basins. This reflects local deformation due to the evolution of the Scotia-Antarctic transcurrent plate boundary and the impact of oceanic spreading along the East Scotia Ridge (ESR). The vertical distribution of the MTDs in the sedimentary record evidences intensified regional tectonic deformation from the middle Miocene to Quaternary. Intensified deformation started at about 15 Ma, when the ESR progressively replaces the West Scotia Ridge (WSR) as the main oceanic spreading center in the Scotia Sea. Coevally with the WSR demise at about 6.5 Ma, increased spreading rates of the ESR and numerous MTDs were formed. The high frequency of MTDs during the Pliocene, mainly along the western basins, is also related to greater tectonic activity due to uplift of the Shackleton Fracture Zone by tectonic inversion and extinction of the Antarctic-Phoenix Ridge and involved changes at late Pliocene. The presence of MTDs in the southern Scotia Sea basins is a relevant indicator of the interplay between sedimentary instability and regional tectonics.
Survey explores active tectonics in northeastern Caribbean

USGS Publications Warehouse

Carbó, A.; Córdoba, D.; Muñoz-Martín, A.; Granja, J.L.; Martín-Dávila, J.; Pazos, A.; Catalán, M.; Gómez, M.; ten Brink, Uri S.; von Hillebrandt, Christa; Payero, J.

2005-01-01

There is renewed interest in studying the active and complex northeastern Caribbean plate boundary to better understand subduction zone processes and for earthquake and tsunami hazard assessments [e.g., ten Brink and Lin, 2004; ten Brink et al., 2004; Grindlay et al., 2005]. To study the active tectonics of this plate boundary, the GEOPRICO-DO (Geological, Puerto Rico-Dominican) marine geophysical cruise, carried out between 28 March and 17 April 2005 (Figure 1), studied the active tectonics of this plate boundary.Initial findings from the cruise have revealed a large underwater landslide, and active faults on the seafloor (Figures 2a and 2c). These findings indicate that the islands within this region face a high risk from tsunami hazards, and that local governments should be alerted in order to develop and coordinate possible mitigation strategies.
Copernican tectonic activities in the northwestern Imbrium region of the Moon

NASA Astrophysics Data System (ADS)

Daket, Yuko; Yamaji, Atsushi; Sato, Katsushi

2015-04-01

Mare ridges and lobate scarps are the manifestations of horizontal compression in the shallow part of the Moon. Conventionally, tectonism within mascon basins has been thought to originate from mascon loading which is syndepositional tectonics (e.g., Solomon and Head, 1980). However, Ono et al. (2009) have pointed out that the subsurface tectonic structures beneath some mare ridges in Serenitatis appeared to be formed after the deposition of mare strata. Watters et al. (2010) also reported Copernican lobate scarps. Those young deformations cannot be explained by the mascon loading and are possibly ascribed to global cooling, orbital evolution and/or regional factors. Since mare ridges are topographically larger than lobate scarps, they might have large contribution to the recent contraction. In this study, we estimated until when the tectonic activities of mare ridges lasted in the northwestern Imbrium region. In order to infer the timing of the latest ages of tectonic activities, we used craters dislocated by the thrust faults that run along to the mare ridges in the study area. The ages of dislocated craters indicate the oldest estimate of the latest tectonic activity of the faults, because those craters must have existed during the tectonic activities. The ages of craters are inferred by the degradation levels classified by Trask (1971). We found ~450 dislocated craters in the study area. About 40 of them are smaller than 100 meter in diameter. Sub-hundred-meter-sized craters that still maintain their morphology sharp are classified into Copernican Period. Those small dislocated craters are interspersed all over the region, indicating that the most of the mare ridges in the study area were tectonically active in Copernican Period. In addition, we also found two sub-hundred-meter-sized craters dislocated by a graben at the west of Promontorium Laplace, indicating horizontal extension existed at Copernican Period. Consequently, tectonic activities in the study
Iapetus: Tectonic structure and geologic history

NASA Technical Reports Server (NTRS)

Croft, Steven K.

1991-01-01

Many papers have been written about the surface of Iapetus, but most of these have discussed either the nature of the strongly contrasting light and dark materials or the cratering record. Little has been said about other geologic features on Iapetus, such as tectonic structures, which would provide constraints on Iapetus' thermal history. Most references have suggested that there is no conclusive evidence for any tectonic activity, even when thermal history studies indicate that there should be. However, a new study of Iapetus' surface involving the use of stereo pairs, an extensive tectonic network has been recognized. A few new observations concerning the craters and dark material were also made. Thus the geology and geologic history of Iapetus can be more fully outlined than before. The tectonic network is shown along with prominent craters and part of the dark material in the geologic/tectonic sketch map. The topology of crater rims and scarps are quite apparent and recognizable in the different image pairs. The heights and slopes of various features given are based on comparison with the depths of craters 50 to 100 km in diameter, which are assumed to have the same depths as craters of similar diameter on Rhea and Titania.
Structural features of northern Tarim basin: Implications for regional tectonics and petroleum traps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong Jia; Juafu Lu; Dongsheng Cai

1998-01-01

The rhombus-shaped Tarim basin in northwestern China is controlled mainly by two left-lateral strike-slip systems: the northeast-trending Altun fault zone along its southeastern side and the northeast-trending Aheqi fault zone along its northwestern side. In this paper, we discuss the northern Tarim basin`s structural features, which include three main tectonic units: the Kalpin uplift, the Kuqa depression, and the North Tarim uplift along the northern margin of the Tarim basin. Structural mapping in the Kalpin uplift shows that a series of imbricated thrust sheets have been overprinted by strike-slip faulting. The amount of strike-slip displacement is estimated to be 148more » km by restoration of strike-slip structures in the uplift. The Kuqa depression is a Mesozoic-Cenozoic foredeep depression with well-developed flat-ramp structures and fault-related folds. The Baicheng basin, a Quaternary pull-apart basin, developed at the center of the Kuqa depression. Subsurface structures in the North Tarim uplift can be divided into the Mesozoic-Cenozoic and the Paleozoic lithotectonic sequences in seismic profiles. The Paleozoic litho-tectonic sequence exhibits the interference of earlier left-lateral and later right-lateral strike-slip structures. Many normal faults in the Mesozoic-Cenozoic litho-tectonic sequence form the negative flower structures in the North Tarim uplift; these structures commonly directly overlie the positive flower structures in the Paleozoic litho-tectonic sequence. The interference regions of the northwest-trending and northeast-trending folds in the Paleozoic tectonic sequence have been identified to have the best trap structures. Our structural analysis indicates that the Tarim basin is a transpressional foreland basin rejuvenated during the Cenozoic.« less
Hydrothermal fluids circulation and travertine deposition in an active tectonic setting: Insights from the Kamara geothermal area (western Anatolia, Turkey)

NASA Astrophysics Data System (ADS)

Brogi, Andrea; Alçiçek, M. Cihat; Yalçıner, Cahit Çağlar; Capezzuoli, Enrico; Liotta, Domenico; Meccheri, Marco; Rimondi, Valentina; Ruggieri, Giovanni; Gandin, Anna; Boschi, Chiara; Büyüksaraç, Aydin; Alçiçek, Hülya; Bülbül, Ali; Baykara, Mehmet Oruç; Shen, Chuan-Chou

2016-06-01

Coexistence of thermal springs, travertine deposits and tectonic activity is a recurring feature for most geothermal areas. Although such a certainty, their relationships are debated mainly addressing on the role of the tectonic activity in triggering and controlling fluids flow and travertine deposition. In this paper, we present the results of an integrated study carried out in a geothermal area located in western Anatolia (Turkey), nearby the well-known Pamukkale area (Denizli Basin). Our study focused on the relationships among hydrothermal fluids circulation, travertine deposition and tectonic activity, with particular emphasis on the role of faults in controlling fluids upwelling, thermal springs location and deposition of travertine masses. New field mapping and structural/kinematics analyses allowed us to recognize two main faults systems (NW- and NE-trending), framed in the Neogene-Quaternary extensional tectonic evolution of western Anatolia. A geo-radar (GPR) prospection was also provided in a key-area, permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure-ridge travertine deposit (Kamara fissure-ridge). The integration among structural and geophysical studies, fluids inclusion, geochemical, isotopic data and 230 Th/238 U radiometric age determination on travertine deposits, depict the characteristics of the geothermal fluids and their pathway, up to the surface. Hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling. As a main conclusion we found strict relationships among tectonic activity, earthquakes occurrence, and variation of the physical/chemical features of the hydrothermal fluids, presently exploited at depth, or flowing out in thermal springs. In the same way, we underline the tectonic role in controlling the travertine deposition, making travertine (mainly banded travertine) a useful proxy to reconstruct the
Counter-intuitive features of the dynamic topography unveiled by tectonically realistic 3D numerical models of mantle-lithosphere interactions

NASA Astrophysics Data System (ADS)

Burov, Evgueni; Gerya, Taras

2013-04-01

It has been long assumed that the dynamic topography associated with mantle-lithosphere interactions should be characterized by long-wavelength features (> 1000 km) correlating with morphology of mantle flow and expanding beyond the scale of tectonic processes. For example, debates on the existence of mantle plumes largely originate from interpretations of expected signatures of plume-induced topography that are compared to the predictions of analytical and numerical models of plume- or mantle-lithosphere interactions (MLI). Yet, most of the large-scale models treat the lithosphere as a homogeneous stagnant layer. We show that in continents, the dynamic topography is strongly affected by rheological properties and layered structure of the lithosphere. For that we reconcile mantle- and tectonic-scale models by introducing a tectonically realistic continental plate model in 3D large-scale plume-mantle-lithosphere interaction context. This model accounts for stratified structure of continental lithosphere, ductile and frictional (Mohr-Coulomb) plastic properties and thermodynamically consistent density variations. The experiments reveal a number of important differences from the predictions of the conventional models. In particular, plate bending, mechanical decoupling of crustal and mantle layers and intra-plate tension-compression instabilities result in transient topographic signatures such as alternating small-scale surface features that could be misinterpreted in terms of regional tectonics. Actually thick ductile lower crustal layer absorbs most of the "direct" dynamic topography and the features produced at surface are mostly controlled by the mechanical instabilities in the upper and intermediate crustal layers produced by MLI-induced shear and bending at Moho and LAB. Moreover, the 3D models predict anisotropic response of the lithosphere even in case of isotropic solicitations by axisymmetric mantle upwellings such as plumes. In particular, in presence of
Lasting mantle scars lead to perennial plate tectonics.

PubMed

Heron, Philip J; Pysklywec, Russell N; Stephenson, Randell

2016-06-10

Mid-ocean ridges, transform faults, subduction and continental collisions form the conventional theory of plate tectonics to explain non-rigid behaviour at plate boundaries. However, the theory does not explain directly the processes involved in intraplate deformation and seismicity. Recently, damage structures in the lithosphere have been linked to the origin of plate tectonics. Despite seismological imaging suggesting that inherited mantle lithosphere heterogeneities are ubiquitous, their plate tectonic role is rarely considered. Here we show that deep lithospheric anomalies can dominate shallow geological features in activating tectonics in plate interiors. In numerical experiments, we found that structures frozen into the mantle lithosphere through plate tectonic processes can behave as quasi-plate boundaries reactivated under far-field compressional forcing. Intraplate locations where proto-lithospheric plates have been scarred by earlier suturing could be regions where latent plate boundaries remain, and where plate tectonics processes are expressed as a 'perennial' phenomenon.
Lasting mantle scars lead to perennial plate tectonics

PubMed Central

Heron, Philip J.; Pysklywec, Russell N.; Stephenson, Randell

2016-01-01

Mid-ocean ridges, transform faults, subduction and continental collisions form the conventional theory of plate tectonics to explain non-rigid behaviour at plate boundaries. However, the theory does not explain directly the processes involved in intraplate deformation and seismicity. Recently, damage structures in the lithosphere have been linked to the origin of plate tectonics. Despite seismological imaging suggesting that inherited mantle lithosphere heterogeneities are ubiquitous, their plate tectonic role is rarely considered. Here we show that deep lithospheric anomalies can dominate shallow geological features in activating tectonics in plate interiors. In numerical experiments, we found that structures frozen into the mantle lithosphere through plate tectonic processes can behave as quasi-plate boundaries reactivated under far-field compressional forcing. Intraplate locations where proto-lithospheric plates have been scarred by earlier suturing could be regions where latent plate boundaries remain, and where plate tectonics processes are expressed as a ‘perennial' phenomenon. PMID:27282541
10 CFR 960.4-2-7 - Tectonics.

Code of Federal Regulations, 2013 CFR

2013-01-01

... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting may...
10 CFR 960.4-2-7 - Tectonics.

Code of Federal Regulations, 2014 CFR

2014-01-01

... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting may...
10 CFR 960.4-2-7 - Tectonics.

Code of Federal Regulations, 2012 CFR

2012-01-01

... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting may...
10 CFR 960.4-2-7 - Tectonics.

Code of Federal Regulations, 2011 CFR

2011-01-01

... activity within the geologic setting during the Quaternary Period. (2) Historical earthquakes within the... isolation. (3) Indications, based on correlations of earthquakes with tectonic processes and features, that either the frequency of occurrence or the magnitude of earthquakes within the geologic setting may...
Preliminary correlations of MAGSAT anomalies with tectonic features of Africa

USGS Publications Warehouse

Hastings, David A.

1982-01-01

An overview of the MAGSAT scalar anomaly map for Africa has suggested a correlation of MAGSAT anomalies with major crustal blocks of uplift or depression and different degrees of regional metamorphism. The strongest MAGSAT anomalies in Africa are closely correlated spatially with major tectonic features. Although a magnetic anomaly caused by a rectangular crustal block would be offset from the block's center by the effects of magnetic inclination, an anomaly caused by real crustal blocks of varying uplift, depression, and degree of regional metamorphism would be located nearer to the locus of greatest vertical movement and highest grade of metamorphism. Thus, the Bangui anomaly may be caused by a central old Precambrian shield, flanked to the north and south by two relatively young sedimentary basins.
Tectonic models for Yucca Mountain, Nevada

USGS Publications Warehouse

O'Leary, Dennis W.

2006-01-01

Performance of a high-level nuclear waste repository at Yucca Mountain hinges partly on long-term structural stability of the mountain, its susceptibility to tectonic disruption that includes fault displacement, seismic ground motion, and igneous intrusion. Because of the uncertainty involved with long-term (10,000 yr minimum) prediction of tectonic events (e.g., earthquakes) and the incomplete understanding of the history of strain and its mechanisms in the Yucca Mountain region, a tectonic model is needed. A tectonic model should represent the structural assemblage of the mountain in its tectonic setting and account for that assemblage through a history of deformation in which all of the observed deformation features are linked in time and space. Four major types of tectonic models have been proposed for Yucca Mountain: a caldera model; simple shear (detachment fault) models; pure shear (planar fault) models; and lateral shear models. Most of the models seek to explain local features in the context of well-accepted regional deformation mechanisms. Evaluation of the models in light of site characterization shows that none of them completely accounts for all the known tectonic features of Yucca Mountain or is fully compatible with the deformation history. The Yucca Mountain project does not endorse a preferred tectonic model. However, most experts involved in the probabilistic volcanic hazards analysis and the probabilistic seismic hazards analysis preferred a planar fault type model. ?? 2007 Geological Society of America. All rights reserved.
10 CFR 960.5-2-11 - Tectonics.

Code of Federal Regulations, 2013 CFR

2013-01-01

... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site during...
10 CFR 960.5-2-11 - Tectonics.

Code of Federal Regulations, 2010 CFR

2010-01-01

... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site during...

10 CFR 960.5-2-11 - Tectonics.

Code of Federal Regulations, 2011 CFR

2011-01-01

... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site during...
10 CFR 960.5-2-11 - Tectonics.

Code of Federal Regulations, 2012 CFR

2012-01-01

... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site during...
10 CFR 960.5-2-11 - Tectonics.

Code of Federal Regulations, 2014 CFR

2014-01-01

... of active faulting within the geologic setting. (2) Historical earthquakes or past man-induced... design limits. (3) Evidence, based on correlations of earthquakes with tectonic processes and features, (e.g., faults) within the geologic setting, that the magnitude of earthquakes at the site during...
Problems of the active tectonics of the Eastern Black Sea

NASA Astrophysics Data System (ADS)

Javakhishvili, Z.; Godoladze, T.; Dreger, D. S.; Mikava, D.; Tvaliashvili, A.

2016-12-01

The Black Sea Basin is the part of the Arabian Eurasian Collision zone and important unit for understanding the tectonic process of the region. This complex basin comprises two deep basins, separated by the mid-Black Sea Ridge. The basement of the Black Sea includes areas with oceanic and continental crust. It was formed as a "back-arc" basin over the subduction zone during the closing of the Tethys Ocean. In the past decades the Black Sea has been the subject of intense geological and geophysical studies. Several papers were published about the geological history, tectonics, basement relief and crustal and upper mantle structure of the basin. New tectonic schemes were suggested (e. g. Nikishin et al 2014, Shillington et al. 2008, Starostenko et al. 2004 etc.). Nevertheless, seismicity of the Black Sea is poorly studied due to the lack of seismic network in the coastal area. It is considered, that the eastern basin currently lies in a compressional setting associated with the uplift of the Caucasus and structural development of the Caucasus was closely related to the evolution of the Eastern Black Sea Basin. Analyses of recent sequence of earthquakes in 2012 can provide useful information to understand complex tectonic structure of the Eastern Black Sea region. Right after the earthquake of 2012/12/23, National Seismic monitoring center of Georgia deployed additional 4 stations in the coastal area of the country, close to the epicenter area, to monitor aftershock sequence. Seismic activity in the epicentral area is continuing until now. We have relocated approximately 1200 aftershocks to delineate fault scarf using data from Georgian, Turkish and Russian datacenters. Waveforms of the major events and the aftershocks were inverted for the fault plane solutions of the events. For the inversion were used green's functions, computed using new 1D velocity model of the region. Strike-slip mechanism of the major events of the earthquake sequence indicates extensional
Unraveling Appalachian tectonics: domain analysis of topographic lineaments in Pennsylvania

NASA Astrophysics Data System (ADS)

Karimi, B.; Schon, K.; Nussbaum, G. W.; Storer, N. D.; McGuire, J. L.; Hardcastle, K.

2016-12-01

Litho-tectonic provinces provide different components of a regions' tectonic history, and are identified as spatial entities with common structural elements, or a number of contiguous related elements. The province boundaries are easily identified when geomorphic expressions are distinct, or significant rock exposure allows for little uncertainty. When exposures are limited, locations of boundaries between provinces are uncertain. In such instances, satellite imagery can be quite advantageous, as tectonically sourced features (faults, folds, fractures, and joints) may exert a strong control on topographic patterns by creating pathways for weathering and erosion. Lineament analyses of topography often focus on well-pronounced tectonic features to interpret regional tectonics. We suggest that lineament analyses including all topographic features may include more subtle tectonic features, resulting in the identification of minor heterogeneities within litho-tectonic provinces. Our study focuses on Appalachian tectonics, specifically in Pennsylvania (PA), home to the Appalachian Orocline and 5 distinct tectonic provinces. Using hillshades from a digital elevation model (DEM) of PA, we manually pick all topographic lineaments 1 km or greater, discriminating only against man-made structures. The final lineament coverage of the state is subdivided into smaller areas for which rose diagrams were prepared. The dominant lineament trends were compared and associated with known structural features. Peaks with no known source are marked as possible tectonic features requiring further research. A domain analysis is performed on the lineament data to identify the extent and interplay of swarms, followed by an investigation of their azimuthal compatibility. We present the results of our domain analysis of all topographic lineaments in the context of identifying litho-tectonic provinces associated with Appalachian tectonics in Pennsylvania, and possible heterogeneities within them.
Influence of Tectonics on the Channel Pattern of Alaknanda River in Srinagar Valley (Garhwal Himalaya)

NASA Astrophysics Data System (ADS)

Datt, Devi

2017-04-01

This paper describes the results of a continuing investigation of tectonic influence on channel pattern and morphology of Alaknanda River in Lesser Garhwal Himalaya, Uttarakhand, India. Extensive field investigations using conventional methods supported by topographical sheets and remote sensing data (LISS IV), were undertaken.The results are classified into three sections :- tectonics, channel pattern and impact of tectonics on channel pattern. The channel length is divided into 8 meanders sets of 3 segments from Supana to Kirtinagar. Thereafter, a litho-tectonic map of the Srinagar valley was prepared. The style of active tectonics on deformation and characterization of fluvial landscape was investigated on typical strike-slip transverse faults near the zone of North Almora Thrust (NAT). NAT is a major tectonic unit of the Lesser Himalaya which passes through the northern margin from NW to SE direction.. The structural and lithological controls on the Alaknanda River system in Srinagar valley are reflected on distinct drainage patterns, abrupt change in flow direction, incised meandering, offset river channels, straight river lines, palaeo-channels, multi levels of terraces, knick points and pools in longitudinal profile. The results of the study show that the sinuosity index of the river is 1.35. Transverse faulting is very common along the NAT. An earlier generation of linear tectonic features were displaced by the latter phase of deformation. Significant deviations were observed in river channel at deformation junctions. Moreover, all 8 sets of meanders are strongly influenced by tectonic features. The meandering course is, thereby, correlated with tectonic features. It is shown that the river channel is strongly influenced by the tectonic features in the study area. Key Words: Tectonic, Meander, Channel pattern, deformation, Knick point.
Hot-spot tectonics on Io

NASA Technical Reports Server (NTRS)

Mcewen, A. S.

1985-01-01

The thesis is that extensional tectonics and low-angle detachment faults probably occur on Io in association with the hot spots. These processes may occur on a much shorter timescale on Ion than on Earth, so that Io could be a natural laboratory for the study of thermotectonics. Furthermore, studies of heat and detachment in crustal extension on Earth and the other terresrial planets (especially Venus and Mars) may provide analogs to processes on Io. The geology of Io is dominated by volcanism and hot spots, most likely the result of tidal heating. Hot spots cover 1 to 2% of Io's surface, radiating at temperatures typically from 200 to 400 K, and occasionally up to 700K. Heat loss from the largest hot spots on Io, such as Loki Patera, is about 300 times the heat loss from Yellowstone, so a tremendous quantity of energy is available for volcanic and tectonic work. Active volcanism on Io results in a resurfacing rate as high as 10 cm per year, yet many structural features are apparent on the surface. Therefore, the tectonics must be highly active.
Episodic Cenozoic volcanism and tectonism in the Andes of Peru

USGS Publications Warehouse

Noble, D.C.; McKee, E.H.; Farrar, E.; Petersen, U.

1974-01-01

Radiometric and geologic information indicate a complex history of Cenozoic volcanism and tectonism in the central Andes. K-Ar ages on silicic pyroclastic rocks demonstrate major volcanic activity in central and southern Peru, northern Chile, and adjacent areas during the Early and Middle Miocene, and provide additional evidence for volcanism during the Late Eocene. A provisional outline of tectonic and volcanic events in the Peruvian Andes during the Cenozoic includes: one or more pulses of igneous activity and intense deformation during the Paleocene and Eocene; a period of quiescence, lasting most of Oligocene time; reinception of tectonism and volcanism at the beginning of the Miocene; and a major pulse of deformation in the Middle Miocene accompanied and followed through the Pliocene by intense volcanism and plutonism. Reinception of igneous activity and tectonism at about the Oligocene-Miocene boundary, a feature recognized in other circum-Pacific regions, may reflect an increase in the rate of rotation of the Pacific plate relative to fixed or quasifixed mantle coordinates. Middle Miocene tectonism and latest Tertiary volcanism correlates with and probably is genetically related to the beginning of very rapid spreading at the East Pacific Rise. ?? 1974.
On the relationship between isostatic elevation and the wavelengths of tectonic surface features on Venus

NASA Technical Reports Server (NTRS)

Zuber, M. T.; Parmentier, E. M.

1990-01-01

Venus lithospheric structure models are presently formulated in which regional isostatic elevation, d, and the spacing wavelength, lambda, of tectonic features formed due to horizontal extension and compression are functions of both surface thermal gradient and crustal thickness c. It is shown that, in areas of Venus where the upper mantle is stronger than the upper crust, the spacings of short-wavelength features should increase with increasing d, if that change in turn is due to increasing c, but should decrease with increasing d, if this change is in turn due to increasing surface thermal gradient.
Charon tectonics

PubMed Central

Beyer, Ross A.; Nimmo, Francis; McKinnon, William B.; Moore, Jeffrey M.; Binzel, Richard P.; Conrad, Jack W.; Cheng, Andy; Ennico, K.; Lauer, Tod R.; Olkin, C.B.; Robbins, Stuart; Schenk, Paul; Singer, Kelsi; Spencer, John R.; Stern, S. Alan; Weaver, H.A.; Young, L.A.; Zangari, Amanda M.

2017-01-01

New Horizons images of Pluto’s companion Charon show a variety of terrains that display extensional tectonic features, with relief surprising for this relatively small world. These features suggest a global extensional areal strain of order 1% early in Charon’s history. Such extension is consistent with the presence of an ancient global ocean, now frozen. PMID:28919640
Geomorphic indices indicated differential active tectonics of the Longmen Shan

NASA Astrophysics Data System (ADS)

Gao, M.; Xu, X.; Tan, X.

2012-12-01

The Longmen Shan thrust belt is located at the eastern margin of the Tibetan Plateau. It is a region of rapid active tectonics with high erosion rates and dense vegetation. The structure of the Longmen Shan region is dominated by northeast-trending thrusts and overturned folds that verge to the east and southeast (Burchfiel et al. 1995, Chen and Wilson 1996). The Longmen Shan thrust belt consists of three major faults from west to east: back-range fault, central fault, and frontal-range fault. The Mw 7.9 Wenchuan earthquake ruptured two large thrust faults along the Longmen Shan thrust belt (Xiwei et al., 2009). In this paper, we focus on investigating the spatial variance of tectonic activeness from the back-range fault to the frontal-range fault, particular emphasis on the differential recent tectonic activeness reflected by the hypsometry and the asymmetric factor of the drainage. Results from asymmetric factor indicate the back-rannge thrust fault on the south of the Maoxian caused drainage basins tilted on the hanging wall. For the north of the Maoxian, the strike-slip fault controlled the shapes of the drainage basins. Constantly river capture caused the expansion of the drainage basins which traversed by the fault. The drainages on the central fault and the frontal-range fault are also controlled by the fault slip. The drainage asymmetric factor suggested the central and southern segments of the Longmen Shan are more active than the northern segment, which is coherence with results of Huiping et al. (2010). The results from hypsometry show the back-range fault is the most active fault among the three major faults. Central fault is less active than the back-range fault but more active than the frontal-range fault. Beichuan is identified as the most active area along the central fault. Our geomorphic indices reflect an overall eastward decreasing of tectonic activeness of the Longmen Shan thrust belt.
Constraints on the lithospheric structure of Venus from mechanical models and tectonic surface features

NASA Technical Reports Server (NTRS)

Zuber, Maria T.

1987-01-01

The evidence for the extensional or compressional origins of some prominent Venusian surface features disclosed by radar images is discussed. Using simple models, the hypothesis that the observed length scales (10-20 km and 100-300 km) of deformations are controlled by dominant wavelengths arising from unstable compression or extension of the Venus lithosphere is tested. The results show that the existence of tectonic features that exhibit both length scales can be explained if, at the time of deformation, the lithosphere consisted of a crust that was relatively strong near the surface and weak at its base, and an upper mantle that was stronger than or nearly comparable in strength to the upper crust.
Tectonics and Volcanism of East Africa as Seen Using Remote Sensing Imagery

NASA Technical Reports Server (NTRS)

Hutt, Duncan John

1996-01-01

The East African Rift is the largest area of active continental geology. The tectonics of this area has been studied with remote sensing data, including AVHRR, Landsat MSS and TM, SPOT, and electronic still camera from Shuttle. Lineation trends have been compared to centers of volcanic and earthquake activity as well as the trends shown on existing geologic maps. Remote sensing data can be used effectively to reveal and analyze significant tectonic features in this area.
Basement Structure and Styles of Active Tectonic Deformation in Central Interior Alaska

NASA Astrophysics Data System (ADS)

Dixit, N.; Hanks, C.

2017-12-01

Central Interior Alaska is one of the most seismically active regions in North America, exhibiting a high concentration of intraplate earthquakes approximately 700 km away from the southern Alaska subduction zone. Based on increasing seismological evidence, intraplate seismicity in the region does not appear to be uniformly distributed, but concentrated in several discrete seismic zones, including the Nenana basin and the adjacent Tanana basin. Recent seismological and neotectonics data further suggests that these seismic zones operate within a field of predominantly pure shear driven primarily by north-south crustal shortening. Although the location and magnitude of the seismic activity in both basins are well defined by a network of seismic stations in the region, the tectonic controls on intraplate earthquakes and the heterogeneous nature of Alaska's continental interior remain poorly understood. We investigated the current crustal architecture and styles of tectonic deformation of the Nenana and Tanana basins using existing geological, geophysical and geochronological datasets. The results of our study demonstrate that the basements of the basins show strong crustal heterogeneity. The Tanana basin is a relatively shallow (up to 2 km) asymmetrical foreland basin with its southern, deeper side controlled by the northern foothills of the central Alaska Range. Northeast-trending strike-slip faults within the Tanana basin are interpreted as a zone of clockwise crustal block rotation. The Nenana basin has a fundamentally different geometry; it is a deep (up to 8 km), narrow transtensional pull-apart basin that is deforming along the left-lateral Minto Fault. This study identifies two distinct modes of tectonic deformation in central Interior Alaska at present, and provides a basis for modeling the interplay between intraplate stress fields and major structural features that potentially influence the generation of intraplate earthquakes in the region.
Tectonic histories between Alba Patera and Syria Planum, Mars

USGS Publications Warehouse

Anderson, R.C.; Dohm, J.M.; Haldemann, A.F.C.; Hare, T.M.; Baker, V.R.

2004-01-01

Syria Planum and Alba Patera are two of the most prominent features of magmatic-driven activity identified for the Tharsis region and perhaps for all of Mars. In this study, we have performed a Geographic Information System-based comparative investigation of their tectonic histories using published geologic map information and Mars Orbiter Laser Altimetry (MOLA) data. Our primary objective is to assess their evolutional histories by focusing on their extent of deformation in space and time through stratigraphic, paleotectonic, topographic, and geomorphologic analyses. Though there are similarities among the two prominent features, there are several distinct differences, including timing deformational extent, and tectonic intensity of formation. Whereas Alba Patera displays a major pulse of activity during the Late Hesperian/Early Amazonian, Syria Planum is a long-lived center that displays a more uniform distribution of simple graben densities ranging from the Noachian to the Amazonian, many of which occur at greater distances away from the primary center of activity. The histories of the two features presented here are representative of the complex, long-lived evolutional history of Tharsis. ?? 2004 Elsevier Inc. All rights reserved.
Implications for the tectonic transition zone of active orogeny in Hoping drainage basin, by landscape evolution at the multi-temporal timescale

NASA Astrophysics Data System (ADS)

Chang, Q.; Chen, R. F.; Lin, W.; Hsieh, P. S.

2015-12-01

In an actively orogeny the landscape are transient state of disequilibrium in response to climatic and tectonic inputs. At the catchment scale, sensitivity of river systems plays an important role in landscape evolution. Hoping drainage basin is located at the tectonic transition zone in the north-eastern Taiwan, where the behavior of Philippine Sea plate switches from overriding above the east-dipping Eurasian Continental plate to northward subducting under the Ryukyu arc. However, extensive deep-seated landslides, debris flow, and numerous large alluvial terraces can be observed, suggesting strong surface processes in this watershed. This effect on regional climate fundamentally changed the landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. In this study we review the morphological evidence from multi-temporal timescale, including in-situ cosmogenic nuclides denudation rate and suspension load data, coupled with the analysis of the longitudinal profiles. The main goal of this study is to compare Holocene erosion rates with thermochronology and radiometric dating of river terraces to investigate the erosion history of Hoping area. The result shows that short-term erosion rate is around twice as large as the long-term denudation rate, which might due to the climate-driven erosion events such as typhoon-induced landslide. We've also mapped detail morphological features by using the high-resolution LiDAR image, which help us to identify not only the landslide but also tectonic features such as lineation, fault scarps, and fracture zones. The tectonic surface features and field investigation results show that the drainage basin is highly fractured, suggesting that even though the vertical tectonic activity rate is small, the horizontal shortening influenced by both southward opening of the back-arc Okinawa trough and the north-western collision in this area is significant. This might cause the reducing in rock strength
Diversity dynamics of Miocene mammals in relation to the history of tectonism and climate

PubMed Central

Finarelli, John A.; Badgley, Catherine

2010-01-01

Continental biodiversity gradients result not only from ecological processes, but also from evolutionary and geohistorical processes involving biotic turnover in landscape and climatic history over millions of years. Here, we investigate the evolutionary and historical contributions to the gradient of increasing species richness with topographic complexity. We analysed a dataset of 418 fossil rodent species from western North America spanning 25 to 5 Ma. We compared diversification histories between tectonically active (Intermontane West) and quiescent (Great Plains) regions. Although diversification histories differed between the two regions, species richness, origination rate and extinction rate per million years were not systematically different over the 20 Myr interval. In the tectonically active region, the greatest increase in originations coincided with a Middle Miocene episode of intensified tectonic activity and global warming. During subsequent global cooling, species richness declined in the montane region and increased on the Great Plains. These results suggest that interactions between tectonic activity and climate change stimulate diversification in mammals. The elevational diversity gradient characteristic of modern mammalian faunas was not a persistent feature over geologic time. Rather, the Miocene rodent record suggests that the elevational diversity gradient is a transient feature arising during particular episodes of Earth's history. PMID:20427339
Topographyc metrics in the southern sector of the Marche foothills: implication for active tectonic analysis

NASA Astrophysics Data System (ADS)

Materazzi, Marco; Aringoli, Domenico; Carducci, Tamara; Cavitolo, Paolo; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

2016-04-01

Quantitative geomorphic analysis can be provided a useful contribution to the study of recent tectonics. Some parameters, that quantify the channels morphology, as the Stream Length-Gradient (SL) Index (Hack, 1973) and the Steepness (Ks) Index (Flint, 1974), are generally used to detect anomalies on the expected concave-up equilibrium stream-profile, which can result in local abrupt changes in stream gradient (i.e., knickpoints) and/or broad convexities on stream long-profiles extending for tens of kilometres (i.e., knickzones). The main goal of this work is the study of the morphological and morphometrical features in the southern sector of the Marche Region, with the aim to gain new knowledge on the influences of rock resistance and rock uplift on the fluvial and topographic system. The investigated area is situated in central Italy and it extends from the axial zone of the Umbria-Marche Apennines to the Adriatic Sea, including the southern sector of the Marche Region and belongs to the foredeep domain of the Apennines orogenic system, which has affected by tectonic activity up to very recent times. The rheology of outcropping deposits doesn't allow the strain to be easily recorded at the outcrop scale. The analyses have been aimed at to test the sensitivity of both SL and Ks for evaluating active crustal deformations, acting at different wavelengths on land surface, within a low tectonically active thrust-and-fold belt. Additional purpose was the understanding of the pattern of regional differential crustal activity in the topographic arrangement of the study area In this research project two sets of analysis were conducted. References Hack J.T. 1973. Stream-profile analysis and stream-gradient index. Journal of Research of the U.S. Geological Survey, 1, 421-429. Flint J.J. 1974. Stream gradient as a function of order, magnitude and discharge. Water Resources Research, 10, 969-973.
Inferring tectonic activity using drainage network and RT model: an example from the western Himalayas, India

NASA Astrophysics Data System (ADS)

Sahoo, Ramendra; Jain, Vikrant

2017-04-01

Morphology of the landscape and derived features are regarded to be an important tool for inferring about tectonic activity in an area, since surface exposures of these subsurface processes may not be available or may get eroded away over time. This has led to an extensive research in application of the non-planar morphological attributes like river long profile and hypsometry for tectonic studies, whereas drainage network as a proxy for tectonic activity has not been explored greatly. Though, significant work has been done on drainage network pattern which started in a qualitative manner and over the years, has evolved to incorporate more quantitative aspects, like studying the evolution of a network under the influence of external and internal controls. Random Topology (RT) model is one of these concepts, which elucidates the connection between evolution of a drainage network pattern and the entropy of the drainage system and it states that in absence of any geological controls, a natural population of channel networks will be topologically random. We have used the entropy maximization principle to provide a theoretical structure for the RT model. Furthermore, analysis was carried out on the drainage network structures around Jwalamukhi thrust in the Kangra reentrant in western Himalayas, India, to investigate the tectonic activity in the region. Around one thousand networks were extracted from the foot-wall (fw) and hanging-wall (hw) region of the thrust sheet and later categorized based on their magnitudes. We have adopted the goodness of fit test for comparing the network patterns in fw and hw drainage with those derived using the RT model. The null hypothesis for the test was, the drainage networks in the fw are statistically more similar than those on the hw, to the network patterns derived using the RT model for any given magnitude. The test results are favorable to our null hypothesis for networks with smaller magnitudes (< 9), whereas for larger
Using the salt tectonics as a proxy to reveal post-rift active crustal tectonics: The example of the Eastern Sardinian margin

NASA Astrophysics Data System (ADS)

Lymer, Gaël; Vendeville, Bruno; Gaullier, Virginie; Chanier, Frank; Gaillard, Morgane

2017-04-01

The Western Tyrrhenian Basin, Mediterranean Sea, is a fascinating basin in terms of interactions between crustal tectonics, salt tectonics and sedimentation. The METYSS (Messinian Event in the Tyrrhenian from Seismic Study) project is based on 2100 km of HR seismic data acquired in 2009 and 2011 along the Eastern Sardinian margin. The main aim is to study the Messinian Salinity Crisis (MSC) in the Western Tyrrhenian Basin, but we also investigate the thinning processes of the continental crust and the timing of crustal vertical motions across this complex domain. Our first results allowed us to map the MSC seismic markers and to better constrain the timing of the rifting, which ended before the MSC across the upper and middle parts of the margin. We also evidenced that crustal activity persisted long after the end of rifting. This has been particularly observed on the upper margin, where several normal faults and a surprising compressional structure were recently active. In this study we investigate the middle margin, the Cornaglia Terrace, where the Mobile Unit (MU, mobile Messinian salt) accumulated during the MSC and acts as a décollement. Our goal is to ascertain whether or not crustal tectonics existed after the pre-MSC rift. This is a challenge where the MU is thick, because potential basement deformations could be first accommodated by the MU and therefore would not find any expression in the supra-salt layers (Upper Unit, UU and Plio-Quaternary, PQ). However our investigations clearly reveal interactions between crustal and salt tectonics along the margin. We thus evidence gravity gliding of the salt and its brittle sedimentary cover along basement slopes generated by the post-MSC tilting of some basement blocks bounded by crustal normal faults, formerly due to the rifting. Another intriguing structure also got our interest. It corresponds to a wedge-shaped of MU located in a narrow N-S half graben bounded to the west by a major, east-verging, crustal

Late Pliocene-Quaternary evolution of outermost hinterland basins of the Northern Apennines (Italy), and their relevance to active tectonics

NASA Astrophysics Data System (ADS)

Sani, Federico; Bonini, Marco; Piccardi, Luigi; Vannucci, Gianfranco; Delle Donne, Dario; Benvenuti, Marco; Moratti, Giovanna; Corti, Giacomo; Montanari, Domenico; Sedda, Lorenzo; Tanini, Chiara

2009-10-01

We examine the tectonic evolution and structural characteristics of the Quaternary intermontane Mugello, Casentino, and Sansepolcro basins, in the Northern Apennines fold-and-thrust belt. These basins have been classically interpreted to have developed under an extensional regime, and to mark the extension-compression transition. The results of our study have instead allowed framing the formation of these basins into a compressive setting tied to the activity of backthrust faults at their northeastern margin. Syndepositional activity of these structures is manifested by consistent architecture of sediments and outcrop-scale deformation. After this phase, the Mugello and Sansepolcro basins experienced a phase of normal faulting extending from the middle Pleistocene until Present. Basin evolution can be thus basically framed into a two-phase history, with extensional tectonics superposed onto compressional structures. Analysis of morphologic features has revealed the occurrence of fresh fault scarps and interaction of faulting with drainage systems, which have been interpreted as evidence for potential ongoing activity of normal faults. Extensional tectonics is also manifested by recent seismicity, and likely caused the strong historical earthquakes affecting the Mugello and Sansepolcro basins. Qualitative comparison of surface information with depth-converted seismic data suggests the basins to represent discrete subsiding areas within the seismic belt extending along the axial zone of the Apennines. The inferred chronology of deformation and the timing of activity of normal faults have an obvious impact on the elaboration of seismic hazard models.
Active Tectonics Around Almaty and along the Zailisky Alatau Rangefront

NASA Astrophysics Data System (ADS)

Grützner, C.; Walker, R. T.; Abdrakhmatov, K. E.; Mukambaev, A.; Elliott, A. J.; Elliott, J. R.

2017-10-01

The Zailisky Alatau is a >250 km long mountain range in Southern Kazakhstan. Its northern rangefront around the major city of Almaty has more than 4 km topographic relief, yet in contrast to other large mountain fronts in the Tien Shan, little is known about its Late Quaternary tectonic activity despite several destructive earthquakes in the historical record. We analyze the tectonic geomorphology of the rangefront fault using field observations, differential GPS measurements of fault scarps, historical and recent satellite imagery, meter-scale topography derived from stereo satellite images, and decimeter-scale elevation models from unmanned aerial vehicle surveys. Fault scarps ranging in height from 2 m to >20 m in alluvial fans indicate that surface rupturing earthquakes occurred along the rangefront fault since the Last Glacial Maximum. Minimum estimated magnitudes for those earthquakes are M6.8-7. Radiocarbon dating results from charcoal layers in uplifted river terraces indicate a Holocene slip rate of 1.2-2.2 mm/a. We find additional evidence for active tectonic deformation all along the Almaty rangefront, basinward in the Kazakh platform, and in the interior of the Zailisky mountain range. Our data indicate that the seismic hazard faced by Almaty comes from a variety of sources, and we emphasize the problems related to urban growth into the loess-covered foothills and secondary earthquake effects. With our structural and geochronologic framework, we present a schematic evolution of the Almaty rangefront that may be applicable to similar settings of tectonic shortening in the mountain ranges of Central Asia.
The tectonics of Venus: An overview

NASA Technical Reports Server (NTRS)

Solomon, Sean C.

1992-01-01

While the Pioneer Venus altimeter, Earth-based radar observatories, and the Venera 15-16 orbital imaging radars provided views of large-scale tectonic features on Venus at ever-increasing resolution, the radar images from Magellan constitute an improvement in resolution of at least an order of magnitude over the best previously available. A summary of early Magellan observations of tectonic features on Venus was published, but data available at that time were restricted to the first month of mapping and represented only about 15 percent of the surface of the planet. Magellan images and altimetry are now available for more than 95 percent of the Venus surface. Thus a more global perspective may be taken on the styles and distribution of lithospheric deformation on Venus and their implications for the tectonic history of the planet.
Recent tectonic stress field, active faults and geothermal fields (hot-water type) in China

NASA Astrophysics Data System (ADS)

Wan, Tianfeng

1984-10-01

It is quite probable that geothermal fields of the hot-water type in China do not develop in the absence of recently active faults. Such active faults are all controlled by tectonic stress fields. Using the data of earthquake fault-plane solutions, active faults, and surface thermal manifestations, a map showing the recent tectonic stress field, and the location of active faults and geothermal fields in China is presented. Data collected from 89 investigated prospects with geothermal manifestations indicate that the locations of geothermal fields are controlled by active faults and the recent tectonic stress field. About 68% of the prospects are controlled by tensional or tensional-shear faults. The angle between these faults and the direction of maximum compressive stress is less than 45°, and both tend to be parallel. About 15% of the prospects are controlled by conjugate faults. Another 14% are controlled by compressive-shear faults where the angle between these faults and the direction maximum compressive stress is greater than 45°.
The Pinjaur dun (intermontane longitudinal valley) and associated active mountain fronts, NW Himalaya: Tectonic geomorphology and morphotectonic evolution

NASA Astrophysics Data System (ADS)

Singh, Vimal; Tandon, S. K.

2008-12-01

The Himalayan orogenic belt, formed as a result of collision tectonic processes, shows abundant evidence of neotectonic activity, active tectonics, and the occurrence of historical earthquakes. Its frontal deformation zone is characterized, in some segments, by intermontane longitudinal valleys (duns). Such frontal segments of the Himalaya are marked by the occurrence of multiple mountain fronts. In one such segment of the foothills of the NW Himalaya, the Pinjaur dun is developed and marked by three mountain fronts: MF1A and MF1B associated with the southernmost Himalayan Frontal Thrust (HFT), MF2 associated with the Sirsa fault, and MF3 associated with the Barsar thrust along the southern margin of the relatively higher main part of the sub-Himalaya. Geomorphic responses to the tectonic activity of these and related structural features have been analyzed through the use of geomorphic indices, drainage density, stream longitudinal profiles, drainage anomalies, and hypsometric analysis. Also, fault and fold growth and their expression on landform development was studied using a combination of surface profiles and field observations. The values of valley floor width to height ratio ( Vf) for valleys associated with MF1 ranged between 0.07 and 0.74, and for valleys associated with MF2 ranged from 1.02-5.12. Vf for the four major valleys associated with MF1B ranged from 1.1-1.7. The asymmetry factor for 26 drainage basins related to MF1A indicate these have developed under the influence of a transverse structure. These results taken together with those obtained from the Hack profiles and SL index values, hypsometry, drainage density, and drainage anomalies suggest that the faults associated with the mountain fronts and related structures are active. Active tectonics and neotectonic activity have led to the formation of four surfaces in the Pinjaur dun. In addition, an important drainage divide separating the Sirsa and Jhajara drainage networks also developed in the
The tectonics of Titan: Global structural mapping from Cassini RADAR

USGS Publications Warehouse

Liu, Zac Yung-Chun; Radebaugh, Jani; Harris, Ron A.; Christiansen, Eric H.; Neish, Catherine D.; Kirk, Randolph L.; Lorenz, Ralph D.; ,

2016-01-01

The Cassini RADAR mapper has imaged elevated mountain ridge belts on Titan with a linear-to-arcuate morphology indicative of a tectonic origin. Systematic geomorphologic mapping of the ridges in Synthetic Aperture RADAR (SAR) images reveals that the orientation of ridges is globally E–W and the ridges are more common near the equator than the poles. Comparison with a global topographic map reveals the equatorial ridges are found to lie preferentially at higher-than-average elevations. We conclude the most reasonable formation scenario for Titan’s ridges is that contractional tectonism built the ridges and thickened the icy lithosphere near the equator, causing regional uplift. The combination of global and regional tectonic events, likely contractional in nature, followed by erosion, aeolian activity, and enhanced sedimentation at mid-to-high latitudes, would have led to regional infilling and perhaps covering of some mountain features, thus shaping Titan’s tectonic landforms and surface morphology into what we see today.
Continental tectonics in the aftermath of plate tectonics

NASA Technical Reports Server (NTRS)

Molnar, Peter

1988-01-01

It is shown that the basic tenet of plate tectonics, rigid-body movements of large plates of lithosphere, fails to apply to continental interiors. There, buoyant continental crust can detach from the underlying mantle to form mountain ranges and broad zones of diffuse tectonic activity. The role of crustal blocks and of the detachment of crustal fragments in this process is discussed. Future areas of investigation are addressed.
Activities for Plate Tectonics using GeoMapApp

NASA Astrophysics Data System (ADS)

Goodwillie, A. M.

2016-12-01

The concept of plate tectonics is a fundamental component of our understanding of how Earth works yet authentic, high-quality geoscience data related to plate tectonics may not be readily available to all students. To compound matters, when data is accessible, students may not possess the skills or resources necessary to explore and analyse it. As a result, much emphasis at federal and state level is now placed upon encouraging students to work with more data and more technology more often and more rigourously. Easy-to-use digital platforms offer much potential for promoting inquiry-based learning at all levels of education. GeoMapApp is one such tool. Developed at Columbia University's Lamont-Doherty Earth Observatory, GeoMapApp (http://www.geomapapp.org) is a free resource that integrates a wide range of research-grade geoscience data in one intuitive map-based interface. Simple strategies for data manipulation, visualisation and presentation allow uses to explore the data in meaningful ways. Layering and transparency capabilities further allow learners to use GeoMapApp to compare multiple data sets at once, and high-impact Save Session functionality allows a GeoMapApp project to be saved for sharing or later use. In this presentation, activities related to plate tectonics will be highlighted. One GeoMapApp activity helps students investigate plate boundaries by exploring earthquake and volcano locations. Another requires students to calculate the rate of seafloor spreading using crustal age data in various ocean basins. A third uses the GeoMapApp layering technique to explore the influence of geological forces in shaping the landscape. Each activity shown can be done by students on an individual basis, as pairs, or as groups. Educators report that student use of GeoMapApp fosters an increased sense of data "ownership" amongst students, promotes STEM skills, and provides them with access to authentic research-grade geoscience data using the same cutting
Morphotectonic analysis and GNSS observations for assessment of relative tectonic activity in Alaknanda basin of Garhwal Himalaya, India

NASA Astrophysics Data System (ADS)

Sharma, Gopal; Champati ray, P. K.; Mohanty, S.

2018-01-01

Alaknanda basin in the Garhwal Himalaya, India, is a tectonically active region owing to ongoing crustal deformation, erosion, and depositional processes active in the region. Active tectonics in this region have greatly affected the drainage system and geomorphic expression of topography and provide an ideal natural set up to investigate the influence of tectonic activity resulting from the India-Eurasia collision. We evaluated active tectonics by using high resolution digital elevation model (DEM) based on eight geomorphic indices (stream length gradient index, valley floor width-to-height ratio, hypsometric integral, drainage basin asymmetry, transverse topography symmetry factor, mountain front sinousity index, bifurcation ratio, and basin shape index) and seismicity in eight subbasins of Alaknanda basin. The integrated product, relative tectonic activity index (TAI) map, was classified into three classes such as: 'highly active' with values ranging up to 2.0; 'moderately active' with values ranging from 2.0 to 2.25; and 'less active' with values > 2.25. Further, the results were compared with relatively high crustal movement rate of 41.10 mm/y computed through high precession Global Navigation Satellite System (GNSS) based continuous operating reference station (CORS) data. Thus, we concluded that this new quantitative approach can be used for better characterization and assessment of active seismotectonic regions of the Himalaya and elsewhere.
Piazzi On Ceres and Pacific On Earth Are Tectonically Comparable Features

NASA Astrophysics Data System (ADS)

Kochemasov, G.

Earth is more than 10 times larger than Ceres but the wave planetary tectonics [1] is not perplexed with this. Theorem 1 states that "Celestial bodies are dichotomic". This theorem is valid for bodies of various sizes, compositions and physical states. What is common for all of them that they are moving, moving in non-circular orbits, and rotate. These properties are sufficient for invoking inertia forces making celestial bodies oscillate and acquire a convexo-concave shape. of the recent planetological achievements three should be mentioned particularly as they concern small celestial bodies where general rules of body shaping are expressed very sharply. A small aster- oid 433 Eros, the largest asteroid 1 Ceres and Borrelli comet were studied in different scales but all of them have essential features predicted by the wave planetology. The convexo-concave shape of asteroid Eros (stony, 33 km long) is repeated in comet Bor- relli (icy, 8 km long). Borrelli's convex hemisphere is sharply jagged because of exten- sion. The same is observed on Eros ("saddle") but in a lesser degree. Borrelli's concave strongly contracted hemisphere is a source of a large complexly built tail of expulsion. This extruded material samples interior of the comet and leaves whitish spots in the centre of the concave side. Eros also have many signes of past degassing in a form of regular net of pits (craters); in the centre of the concave side is a large complexly built crater Psych. Both oblong bodies -Eros and Borrelli - have different opposite ends: blunt and sharp, predicted by the wave planetology (the Arctic-Antarctic symp- tom). The oblong body of Ceres (major/minor axes of 898/788 km [2] and 970/ 930 km,[Parker &Stern]) according to HST (J.Parker &Stern) has a prominent dusky dark spot (Piazzi) from one side. It occupies a significant part of the asteroid (about 250 km, more than a quarter the size of Ceres) and probably might be assigned to a depression. Tectonically one may compare
Venusian tectonics: Convective coupling to the lithosphere?

NASA Technical Reports Server (NTRS)

Phillips, R. J.

1987-01-01

The relationship between the dominant global heat loss mechanism and planetary size has motivated the search for tectonic style on Venus. Prior to the American and Soviet mapping missions of the past eight years, it was thought that terrestrial style plate tectonics was operative on Venus because this planet is approximately the size of the Earth and is conjectured to have about the same heat source content per unit mass. However, surface topography mapped by the altimeter of the Pioneer Venus spacecraft did not show any physiographic expression of terrestrial style spreading ridges, trenches, volcanic arcs or transform faults, although the horizontal resolution was questionable for detection of at least some of these features. The Venera 15 and 16 radar missions mapped the northern latitudes of Venus at 1 to 2 km resolution and showed that there are significant geographic areas of deformation seemingly created by large horizontal stresses. These same high resolution images show no evidence for plate tectonic features. Thus a fundamental problem for venusian tectonics is the origin of large horizontal stresses near the surface in the apparent absence of plate tectonics.
The Central-Western Mediterranean: Anomalous igneous activity in an anomalous collisional tectonic setting

NASA Astrophysics Data System (ADS)

Lustrino, Michele; Duggen, Svend; Rosenberg, Claudio L.

2011-01-01

plate (Sardinia, Corsica, Balearic Islands, Kabylies, Calabria, Peloritani Mountains). The bulk of igneous activity in the central-western Mediterranean is believed to have tapped mantle 'wedge' regions, metasomatized by pressure-related dehydration of the subducting slabs. The presence of subduction-related igneous rocks with a wide range of chemical composition has been related to the interplay of several factors among which the pre-metasomatic composition of the mantle wedges (i.e., fertile vs. refractory mineralogy), the composition of the subducting plate (i.e., the type and amount of sediment cover and the alteration state of the crust), the variable thermo-baric conditions of magma formation, coupled with variable molar concentrations of CO 2 and H 2O in the fluid phase released by the subducting plates are the most important. Compared to classic collisional settings (e.g., Himalayas), the central-western Mediterranean area shows a range of unusual geological and magmatological features. These include: a) the rapid formation of extensional basins in an overall compressional setting related to Africa-Europe convergence; b) centrifugal wave of both compressive and extensional tectonics starting from a 'pivotal' region around the Gulf of Lyon; c) the development of concomitant Cenozoic subduction zones with different subduction and tectonic transport directions; d) subduction 'inversion' events (e.g., currently along the Maghrebian coast and in northern Sicily, previously at the southern paleo-European margin); e) a repeated temporal pattern whereby subduction-related magmatic activity gives way to magmas of intraplate geochemical type; f) the late-stage appearance of magmas with collision-related 'exotic' (potassic to ultrapotassic) compositions, generally absent from simple subduction settings; g) the relative scarcity of typical calcalkaline magmas along the Italian peninsula; h) the absence of igneous activity where it might well be expected (e.g., above the
Tectonic Evolution of Bell Regio, Venus: Regional Stress, Lithospheric Flexure, and Edifice Stresses

NASA Astrophysics Data System (ADS)

Rogers, P. G.; Zuber, M. T.

1996-03-01

Analyses of the tectonic features associated with large volcanoes provide important insight into the relationship between volcanic and tectonic processes and the stress state of a planet's crust over time, and provide constraints on the local and regional geologic evolution. This investigation focuses on the tectonism and volcanism of Bell Regio, a major highland uplift n Venus. The stress environments and resulting tectonic features associated with the major volcanic edifices in this region are examined using Magellan ynthetic aperture radar (SAR) images and altimeter measurements of topography. The major volcanoes of Bell Regio, Tepev Mons and the "Eastern Volcanic Center" (EVC), exhibit tectonic characteristics that are unique relative to other volcanic edifices on Venus. The most prominent distinctions are the lack of large rift zones within the overall highland uplift and the presence of radial tectonic and concentric fractures associated with the major edifices. This study examines the regional stress field in Bell Regio through analysis of structural features believed to be a consequence of lithospheric flexure due to volcanic loading and tectonic features that likely resulted from edifice stresses associated with magma chamber inflation.
Relationships between tectonism, volcano-tectonism and volcanism: the Ischia island (Italy) case.

NASA Astrophysics Data System (ADS)

Marotta, E.; de Vita, S.; Orsi, G.; Sansivero, F.

2005-12-01

The resurgent calderas of Ischia, Campi Flegrei and Pantelleria are characterized by differentially displaced blocks, and distribution of later eruption vents in a well defined sector of the resurgent area. These features suggest a simple shearing block resurgence mechanism. Moreover, the studies carried out on Ischia and Campi Flegrei evidenced a very complex structural pattern due to deformation related to the local stress regime induced by magmatism and volcanism and also to reactivation of regional structures. In order to better define the relationships among tectonic, volcano-tectonic and caldera resurgence mechanism, a structural study has been carried out at Ischia, where the Mt. Epomeo has been uplifted of about 900 m in the past 30 ka. The measures taken on 1,400 planar surfaces (faults, joints and fracture cleavages) show that the resurgent area is composed of differentially displaced blocks whose uplifting is maximum for the Mt. Epomeo and decreases southeastward. The resurgent area has a poligonal shape resulting from the reactivation of regional faults and by the activation of faults directly related to volcano-tectonism. The limit of the resurgent area is not defined towards the north, as beach deposits displaced at variable elevation by E-W and NW-SE trending faults, are exposed along the coastline. The western sector is bordered by inward-dipping, high-angle reverse faults, whose directions vary from N40E to NS and N50W from NW to SW of the block, testifying a compressional stress regime active in this area. These features are cut by late outward-dipping normal faults due to gravitational readjustment of the slopes. Vertical faults border the block at NE ad SW with right transtensive and left transpressive movements, respectively. The area located to the east of the most uplifted block, characterized by a tensile stress regime, has been deformed by N-S, N40-70E and N15W trending normal faults, with maximum elongation direction along N50W. The
Quaternary tectonic faulting in the Eastern United States

USGS Publications Warehouse

Wheeler, R.L.

2006-01-01

Paleoseismological study of geologic features thought to result from Quaternary tectonic faulting can characterize the frequencies and sizes of large prehistoric and historical earthquakes, thereby improving the accuracy and precision of seismic-hazard assessments. Greater accuracy and precision can reduce the likelihood of both underprotection and unnecessary design and construction costs. Published studies proposed Quaternary tectonic faulting at 31 faults, folds, seismic zones, and fields of earthquake-induced liquefaction phenomena in the Appalachian Mountains and Coastal Plain. Of the 31 features, seven are of known origin. Four of the seven have nontectonic origins and the other three features are liquefaction fields caused by moderate to large historical and Holocene earthquakes in coastal South Carolina, including Charleston; the Central Virginia Seismic Zone; and the Newbury, Massachusetts, area. However, the causal faults of the three liquefaction fields remain unclear. Charleston has the highest hazard because of large Holocene earthquakes in that area, but the hazard is highly uncertain because the earthquakes are uncertainly located. Of the 31 features, the remaining 24 are of uncertain origin. They require additional work before they can be clearly attributed either to Quaternary tectonic faulting or to nontectonic causes. Of these 24, 14 features, most of them faults, have little or no published geologic evidence of Quaternary tectonic faulting that could indicate the likely occurrence of earthquakes larger than those observed historically. Three more features of the 24 were suggested to have had Quaternary tectonic faulting, but paleoseismological and other studies of them found no evidence of large prehistoric earthquakes. The final seven features of uncertain origin require further examination because all seven are in or near urban areas. They are the Moodus Seismic Zone (Hartford, Connecticut), Dobbs Ferry fault zone and Mosholu fault (New York
Pargo Chasma and its relationship to global tectonics

NASA Technical Reports Server (NTRS)

Ghail, R. C.

1993-01-01

Pargo Chasma was first identified on Pioneer Venus data as a 10,000 km long lineation extending from Atla Regio in the north terminating in the plains south of Phoebe Regio. More recent Magellan data have revealed this feature to be one of the longest chains of coronae so far identified on the planet. Stofan et al have identified 60 coronae and 2 related features associated with this chain; other estimates differ according to the classification scheme adopted, for example Head et al. identify only 29 coronae but 43 arachnoids in the same region. This highlights one of the major problems associated with the preliminary mapping of the Magellan data: there has been an emphasis on identifying particular features on Venus without a universally accepted scheme to classify those features. Nevertheless, Pargo Chasma is clearly identified as a major tectonic belt of global significance. Together with the Artemis-Atla-Beta tectonic zone and the Beta-Phoebe rift belt, Pargo Chasma defines a region on Venus with an unusually high concentration of tectonic and volcanic features. Thus, an understanding of the processes involved in the formation of Pargo Chasma may lend significant insight into the evolution of the region and the planet as a whole. I have produced a detailed 1 to 10 million scale map of Pargo Chasma and the surrounding area from preliminary USGS controlled mosaiced image maps of Venus constructed from Magellan data. In view of the problems highlighted above in relation the efforts already made at identifying a particular set of features I have mapped the region purely on the basis of the geomorphology visible in the magellan data without any attempt at identifying a particular set or class of features. Thus, the map produced distinguishes between areas of different brightness and texture. This has the advantage of highlighting the tectonic fabric of Pargo Chasma and clearly illustrates the close inter-relationship between individual coronae and the surrounding
The revised tectonic history of Tharsis

NASA Astrophysics Data System (ADS)

Bouley, Sylvain; Baratoux, David; Paulien, Nicolas; Missenard, Yves; Saint-Bézar, Bertrand

2018-04-01

Constraining the timing of the emplacement of the volcano-tectonic province of Tharsis is critical to understanding the evolution of mantle, surface environment and climate of Mars. The growth of Tharsis had exerted stresses on the lithosphere, which were responsible for tectonic deformation, previously mapped as radial or concentric faults. Insights into the emplacement history of Tharsis may be gained from an analysis of the characteristics and ages of these tectonic features. The number, total length, linear density of extensional or compressional faults in the Tharsis region and deformation rates are reported for each of the following 6 stages: Early and Middle Noachian (stage 1); Late Noachian (stage 2); Early Hesperian (stage 3); Late Hesperian (stage 4), Early Amazonian (stage 5) and Middle Amazonian to Late Amazonian (stage 6). 8571 Tharsis-related tectonic features (radial or concentric to the center of Tharsis) were assigned to one of these periods of time based on their relationship with stratigraphic units defined in the most recent geological map. Intense faulting at Tempe Terra, Claritas and Coracis Fossae and Thaumasia Planum confirms that tectonic deformation started during the Noachian. However, we report a peak in both compressive and extensive rates of deformation during the Early Hesperian whereas the quantitative indicators for compressional and extensional tectonics vary within less than one order of magnitude from the Late Noachian to the Late Hesperian. These observations indicate a protracted growth of Tharsis during the first quarter of Mars evolution and declining from 3 Gyrs ago.
Eastern Ishtar Terra: Tectonic evolution derived from recognized features

NASA Technical Reports Server (NTRS)

Vorderbruegge, R. W.; Head, James W.

1989-01-01

Previous analyses have recognized several styles and orientations of compressional deformation, crustal convergence, and crustal thickening in Eastern Ishtar Terra. An east to west sense of crustal convergence through small scale folding, thrusting, and buckling is reflected in the high topography and ridge-and-valley morphology of Maxwell Montes and the adjacent portion of Fortuna Tessera. This east to west convergence was accompanied by up to 1000 km of lateral motion and large scale strike-slip faulting within two converging shear zones which has resulted in the present morphology of Maxwell Montes. A more northeast to southwest sense of convergence through large scale buckling and imbrication is reflected in large, northwest-trending scarps along the entire northern boundary of Ishtar Terra, with up to 2 km of relief present at many of the scarps. It was previously suggested that both styles of compression have occurred at the expense of pre-existing tessera regions which have then been overprinted by the latest convergence event. The difference in style is attributed mostly to differences in the properties of the crust converging with the tessera blocks. If one, presumably thick, tessera block converges with another tessera region, then the widespread, distributed style of deformation occurs, as observed in western Fortuna Tessera. However, if relatively thin crust (such as suggested for the North Polar Plains converges with thicker tessera regions, then localized deformation occurs, as reflected in the scarps along Northern Ishtar Terra. The purpose is to identify the types of features observed in Eastern Ishtar Terra. Their potential temporal and spatial relationships, is described, possible origins for them is suggested, and how the interpretation of some of these features has led to the multiple-style tectonic evolution model described is shown.
Vertical tectonics at an active continental margin

NASA Astrophysics Data System (ADS)

Houlié, N.; Stern, T. A.

2017-01-01

Direct observations of vertical movements of the earth's surface are now possible with space-based GPS networks, and have applications to resources, hazards and tectonics. Here we present data on vertical movements of the Earth's surface in New Zealand, computed from the processing of GPS data collected between 2000 and 2015 by 189 permanent GPS stations. We map the geographical variation in vertical rates and show how these variations are explicable within a tectonic framework of subduction, volcanic activity and slow slip earthquakes. Subsidence of >3 mm/yr is observed along southeastern North Island and is interpreted to be due to the locked segment of the Hikurangi subduction zone. Uplift of 1-3 mm/yr further north along the margin of the eastern North Island is interpreted as being due to the plate interface being unlocked and underplating of sediment on the subduction thrust. The Volcanic Plateau of the central North Island is being uplifted at about 1 mm/yr, which can be explained by basaltic melts being injected in the active mantle-wedge at a rate of ∼6 mm/yr. Within the Central Volcanic Region there is a 250 km2 area that subsided between 2005 and 2012 at a rate of up to 14 mm/yr. Time series from the stations located within and near the zone of subsidence show a strong link between subsidence, adjacent uplift and local earthquake swarms.
Mimas: Tectonic structure and geologic history

NASA Technical Reports Server (NTRS)

Croft, Steven K.

1991-01-01

Mimas, the innermost of the major saturnian satellites, occupies an important place in comparative studies of icy satellites. It is the smallest icy satellite known to have a mostly spherical shape. Smaller icy objects like Hyperion and Puck are generally irregular in shape, while larger ones like Miranda and Enceladus are spherical. Thus Mimas is near the diameter where the combination of increasing surface gravity and internal heating begin to have a significant effect on global structure. The nature and extent of endogenic surface features provide important constraints on the interior structure and history of this transitional body. The major landforms on Mimas are impact craters. Mimas has one of the most heavily cratered surfaces in the solar system. The most prominent single feature on Mimas is Herschel, an unrelaxed complex crater 130 km in diameter. The only other recognized landforms on Mimas are tectonic grooves and lineaments. Groove locations were mapped by Schenk, but without analysis of groove structures or superposition relationships. Mimas' tectonic structures are remapped here in more detail than previously has been done, as part of a general study of tectonic features on icy satellites.

Venus tectonics - An overview of Magellan observations

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Smrekar, Suzanne E.; Bindschadler, Duane L.; Grimm, Robert E.; Kaula, William M.; Mcgill, George E.; Phillips, Roger J.; Saunders, R. S.; Schubert, Gerald; Squyres, Steven W.

1992-01-01

Magellan observations of the tectonic characteristics of highland regions on Venus are discussed with reference to competing theories for highland formation and evolution. Complex rigid terrain, or tessera, and the extent to which these elevated blocks of intensely deformed crust may be genetically related to highlands are then considered. Further, the tectonics of plains and lowland regions are examined, including deformation belts and coronae, and possible relations between such features and mantle dynamics. Implications of these observations for the global tectonics of Venus are discussed.
Landscapes of human evolution: models and methods of tectonic geomorphology and the reconstruction of hominin landscapes.

PubMed

Bailey, Geoffrey N; Reynolds, Sally C; King, Geoffrey C P

2011-03-01

This paper examines the relationship between complex and tectonically active landscapes and patterns of human evolution. We show how active tectonics can produce dynamic landscapes with geomorphological and topographic features that may be critical to long-term patterns of hominin land use, but which are not typically addressed in landscape reconstructions based on existing geological and paleoenvironmental principles. We describe methods of representing topography at a range of scales using measures of roughness based on digital elevation data, and combine the resulting maps with satellite imagery and ground observations to reconstruct features of the wider landscape as they existed at the time of hominin occupation and activity. We apply these methods to sites in South Africa, where relatively stable topography facilitates reconstruction. We demonstrate the presence of previously unrecognized tectonic effects and their implications for the interpretation of hominin habitats and land use. In parts of the East African Rift, reconstruction is more difficult because of dramatic changes since the time of hominin occupation, while fossils are often found in places where activity has now almost ceased. However, we show that original, dynamic landscape features can be assessed by analogy with parts of the Rift that are currently active and indicate how this approach can complement other sources of information to add new insights and pose new questions for future investigation of hominin land use and habitats. Copyright © 2010 Elsevier Ltd. All rights reserved.
Morphological expression of active tectonics in the Southern Alps

NASA Astrophysics Data System (ADS)

Robl, Jörg; Heberer, Bianca; Neubauer, Franz; Hergarten, Stefan

2015-04-01

rates are not well constrained for the entire domain. Despite of that, extensive karstification in some areas limits the validity of a morphometric analysis in particular of the upper reaches of the drainage system and leads to a long term persistence of landforms (e.g. plateaus). In this study we focus on the drainage pattern of the eastern Southern Alps and the adjacent southern foreland basin. We use a high-resolution digital elevation model and a novel numerical approach to extract characteristic parameters of the morphology for the entire eastern Southern Alps with a high spatial resolution. We explore deviations in the steepness of channels from an equilibrium state and knick-points in longitudinal channel profiles and interpret these features in terms of (a) active tectonics, and variable uplift rates, (b) lithological effects like erodibility contrasts and karstification, and (c) base level lowering caused by glacial erosion and Messinian preconditioning. The drainage system of the Adige shows the most significant deviations from a fluvial equilibrium. This is documented in the normalized steepness index of the main channel and all tributaries as well as in the longitudinal channel profile. The main channel shows several sections of downstream steepening and extremely low channel gradients in the lower reach. Similar deviations are also observed in the Brenta catchment situated east of the Adige drainage system. In contrast to the two large western catchments of the study region, the Piave and particularly the Tagliamento catchment show well graded channel profiles and uniform normalized steepness indices despite of the glacial history. This clear west to east trend from highly disturbed to overall well graded channels has never been documented before and may be explained in the light of increased uplift rates in the east and differences in onset and timing of topography formation between the western and eastern sector of the study region.
Response of Cenozoic turbidite system to tectonic activity and sea-level change off the Zambezi Delta

NASA Astrophysics Data System (ADS)

Castelino, Jude A.; Reichert, Christian; Jokat, Wilfried

2017-09-01

Submarine fans and turbidite systems are important and sensitive features located offshore from river deltas that archive tectonic events, regional climate, sea level variations and erosional process. Very little is known about the sedimentary structure of the 1800 km long and 400 km wide Mozambique Fan, which is fed by the Zambezi and spreads out into the Mozambique Channel. New multichannel seismic profiles in the Mozambique Basin reveal multiple feeder systems of the upper fan that have been active concurrently or consecutively since Late Cretaceous. We identify two buried, ancient turbidite systems off Mozambique in addition to the previously known Zambezi-Channel system and another hypothesized active system. The oldest part of the upper fan, located north of the present-day mouth of the Zambezi, was active from Late Cretaceous to Eocene times. Regional uplift caused an increased sediment flux that continued until Eocene times, allowing the fan to migrate southwards under the influence of bottom currents. Following the mid-Oligocene marine regression, the Beira High Channel-levee complex fed the Mozambique Fan from the southwest until Miocene times, reworking sediments from the shelf and continental slope into the distal abyssal fan. Since the Miocene, sediments have bypassed the shelf and upper fan region through the Zambezi Valley system directly into the Zambezi Channel. The morphology of the turbidite system off Mozambique is strongly linked to onshore tectonic events and the variations in sea level and sediment flux.
Discriminating Characteristics of Tectonic and Human-Induced Seismicity

NASA Astrophysics Data System (ADS)

Zaliapin, I. V.; Ben-Zion, Y.

2015-12-01

We analyze statistical features of background and clustered subpopulations of earthquakes in different regions in an effort to distinguish between human-induced and natural seismicity. Analysis of "end-member" areas known to be dominated by human-induced earthquakes (the Geyser geothermal field in northern California and TauTona gold mine in South Africa) and regular tectonic activity (the San Jacinto fault zone in southern California and Coso region excluding the Coso geothermal field in eastern central California) reveals several distinguishing characteristics. Induced seismicity is shown to have (i) higher rate of background events (both absolute and relative to the total rate), (ii) faster temporal offspring decay, (iii) higher intensity of repeating events, (iv) larger proportion of small clusters, and (v) larger spatial separation between parent and offspring, compared to regular tectonic activity. These differences also successfully discriminate seismicity within the Coso and Salton Sea geothermal fields in California before and after the expansion of geothermal production during the 1980s.
Areas of Unsolved Problems in Caribbean Active Tectonics

NASA Astrophysics Data System (ADS)

Mann, P.

2015-12-01

I review some unsolved problems in Caribbean active tectonics. At the regional and plate scale: 1) confirm the existence of intraplate deformation zones of the central Caribbean plate that are within the margin of error of ongoing GPS measurements; 2) carry out field studies to evaluate block models versus models for distributed fault shear on the densely populated islands of Jamaica, Hispaniola, Puerto Rico, and the Virgin Islands; 3) carry out paleoseismological research of key plate boundary faults that may have accumulated large strains but have not been previously studied in detail; 4) determine the age of onset and far-field effects of the Cocos ridge and the Central America forearc sliver; 4) investigate the origin and earthquake-potential of obliquely-sheared rift basins along the northern coast of Venezuela; 5) determine the age of onset and regional active, tectonic effects of the Panama-South America collision including the continued activation of the Maracaibo block; and 6) validate longterm rates on active subduction zones with improving, tomographic maps of subducted slabs. At the individual fault scale: 1) determine the mode of termination of large and active strike -slip faults and application of the STEP model (Septentrional, Polochic, El Pilar, Bocono, Santa Marta-Bucaramanaga); 2) improve the understanding of the earthquake potential on the Enriquillo-Plantain Garden fault zone given "off-fault" events such as the 2010 Haiti earthquake; how widespread is this behavior?; and 3) estimate size of future tsunamis from studies of historic or prehistoric slump scars and mass transport deposits; what potential runups can be predicted from this information?; and 4) devise ways to keep rapidly growing, circum-Caribbean urban populations better informed and safer in the face of inevitable and future, large earthquakes.
Tectonic map of Indonesia: A progress report

USGS Publications Warehouse

Hamilton, Warren Bell

1970-01-01

Orogeny, volcanism, and seismicity are now intensely active in Indonesia. Many Dutch tectonists--Brouwer, Umbgrove, van Bemifielen, Smit4Sibinga, Vening Meinesz, Westerveld, and others--recognized that this complex cluster of islands represents an early stage in the evolution of orogenic belts. Not until Indonesia is understood can we comprehend the Alps. This report summarizes some aspects of work to date on the Tectonic Map of Indonesia. The preparation of this map is a joint project of the Geological Survey of Indonesia and the United States Geological Survey, sponsored by the Government of Indonesia and the United States Agency for International Development. The Tectonic Map of Indonesia will be published at a scale of 1:5,000,000. Adjacent regions in other countries will be included to provide a broader context. The map limits presently envisaged are the parallels of 12° N. and 15° S., and the meridians of 91° and 148° E. Tectonic features will be shown in many colors and patterns. Bathymetry is being newly compiled, and will be shown with contours and shades of blue. Figure 1 shows the islands of Indonesia.
Hot-field tectonics

NASA Astrophysics Data System (ADS)

Zonenshain, L. P.; Kuzmin, M. I.; Bocharova, N. Yu.

1991-12-01

Intraplate, hot spot related volcanic occurrences do not have a random distribution on the Earth's surface. They are concentrated in two large regions (up to 10,000 km in diameter), the Pacific and the African, and two smaller areas (2000-3000 km in diameter), the Central Asian and the Tasmanian. These regions are considered as manifestations of hot fields in the mantle, whereas the regions lying in between are expressions of cold fields in the mantle. Large-scale anomalies coincide with the hot fields: topographic swells, geoid highs, uplifts of the "asthenospheric table", inferred heated regions in the lowermost mantle according to seismic tomographic images, geochemical anomalies showing the origin of volcanics from undepleted mantle sources. Hot fields are relatively stable features, having remained in the same position on the Earth's surface during the last 120 Ma, although they have other configurations and other positions in the Late Paleozoic and Early Mesozoic. Available data show that two main hot fields (Pacific and African) are possibly moving one with respect to the other, converging along the Eastern Pacific subduction system and diverging along that of the Western Pacific. If so, well-known differences between these subduction systems can also be connected with related displacement of the hot fields. Hot fields are assumed to correspond to upwelling branches of mantle and rather deep mantle convection, and cold fields to downwelling branches. Thus, hot fields can be regarded as expressions of deeper tectonics, comparative to the plate tectonics, which is operating in the upper layers of the Earth. We call it hot-field tectonics. Plate tectonics is responsible for the opening and closure of oceans and for the formation of orogenic belts, whereas hot-field tectonics accounts for a larger cyclicity of the Earth's evolution and for amalgamation and break up of Pangea-type supercontinents. Hot-field tectonics seems to be the only process to have existed
Geomorphology, active tectonics, and landscape evolution in the Mid-Atlantic region: Chapter

USGS Publications Warehouse

Pazzaglia, Frank J.; Carter, Mark W.; Berti, Claudio; Counts, Ronald C.; Hancock, Gregory S.; Harbor, David; Harrison, Richard W.; Heller, Matthew J.; Mahan, Shannon; Malenda, Helen; McKeon, Ryan; Nelson, Michelle S.; Prince, Phillip; Rittenour, Tammy M.; Spotilla, James; Whittecar, G. Richard

2015-01-01

In 2014, the geomorphology community marked the 125th birthday of one of its most influential papers, “The Rivers and Valleys of Pennsylvania” by William Morris Davis. Inspired by Davis’s work, the Appalachian landscape rapidly became fertile ground for the development and testing of several grand landscape evolution paradigms, culminating with John Hack’s dynamic equilibrium in 1960. As part of the 2015 GSA Annual Meeting, the Geomorphology, Active Tectonics, and Landscape Evolution field trip offers an excellent venue for exploring Appalachian geomorphology through the lens of the Appalachian landscape, leveraging exciting research by a new generation of process-oriented geomorphologists and geologic field mapping. Important geomorphologic scholarship has recently used the Appalachian landscape as the testing ground for ideas on long- and short-term erosion, dynamic topography, glacial-isostatic adjustments, active tectonics in an intraplate setting, river incision, periglacial processes, and soil-saprolite formation. This field trip explores a geologic and geomorphic transect of the mid-Atlantic margin, starting in the Blue Ridge of Virginia and proceeding to the east across the Piedmont to the Coastal Plain. The emphasis here will not only be on the geomorphology, but also the underlying geology that establishes the template and foundation upon which surface processes have etched out the familiar Appalachian landscape. The first day focuses on new and published work that highlights Cenozoic sedimentary deposits, soils, paleosols, and geomorphic markers (terraces and knickpoints) that are being used to reconstruct a late Cenozoic history of erosion, deposition, climate change, and active tectonics. The second day is similarly devoted to new and published work documenting the fluvial geomorphic response to active tectonics in the Central Virginia seismic zone (CVSZ), site of the 2011 M 5.8 Mineral earthquake and the integrated record of Appalachian
Satellite Elevation Magnetic and Gravity Models of Major South American Plate Tectonic Features

NASA Technical Reports Server (NTRS)

Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Lidiak, E. G.; Keller, G. R. (Principal Investigator); Longacre, M. B.

1984-01-01

Some MAGSAT scalar and vector magnetic anomaly data together with regional gravity anomaly data are being used to investigate the regional tectonic features of the South American Plate. An initial step in this analysis is three dimensional modeling of magnetic and gravity anomalies of major structures such as the Andean subduction zone and the Amazon River Aulacogen at satellite elevations over an appropriate range of physical properties using Gaus-Legendre quadrature integration method. In addition, one degree average free-air gravity anomalies of South America and adjacent marine areas are projected to satellite elevations assuming a spherical Earth and available MAGSAT data are processed to obtain compatible data sets for correlation. Correlation of these data sets is enhanced by reduction of the MAGSAT data to radial polarization because of the profound effect of the variation of the magnetic inclination over South America.
Geological timing and duration of methane seepage in different sedimentary and tectonic settings in the Lower Congo Basin

NASA Astrophysics Data System (ADS)

Wenau, S.; Spiess, V.

2016-12-01

Methane seepage sites have been investigated in the Lower Congo Basin using seismo-acoustic methods in combination with geological and geochemical sampling. Pockmarks were observed in different areas of the Lower Congo Basin that are affected by different styles of salt-tectonic deformation and sedimentary input. At the salt front in the southern part of the basin, methane seepage shifts continuously westwards as previously undeformed sediments are affected by westward moving salt. Older seepage sites to the East are cut off from methane supply in the process of continuing salt-tectonic deformation. The initiation of gas accumulation and seepage directly at the deformation front is expected in the late Miocene due to salt-induced uplift. In the northern part of the basin on the lower slope, methane seepage is focused along salt-tectonic faults connecting Pliocene fan deposits to the seafloor, breaching the hemipelagic seal. These sites show indications for continuing seepage for the last 640 kyrs. Such long term seepage activity may be due to the lack of polygonal faults in the hemipelagic seal, focusing gas migration on fewer, salt-tectonic faults. Westward of the salt front, seepage features include the Regab pockmark where a potential reservoir in an Early Pleistocene channel flank is connected to the seafloor feature via a seismic chimney. Seepage activity in this area is also documented to be continuous over geologic time scales by seafloor and sub-seafloor seepage indications such as chimneys, pockmarks and buried seepage features. The Lower Congo Basin thus documents the longevity of seepage processes in the context of various tectonic and sedimentary regimes on a passive continental margin. Indications of the duration of seepage activity at individual sites may be used for methane budgeting in combination with emission rates estimated for typical seepage sites.
Tectonic map of the Arabian Peninsula

USGS Publications Warehouse

Brown, Glen F.

1972-01-01

This tectonic map of the Arabian peninsula, prepared for the Audi Arabian Ministry of Petroleum and Mineral Resource, is the first of a series of peninsular maps that attempt to show regional features. Much recent information resulting from detailed geologic mapping notably within the Arabian craton, from geophysical surveys, both airborne and oceanographic in adjacent seas, from deep exploratory drilling, and from photography from the Gemini and Apollo space programs, has been used in the tectonic evaluation.
Tectonic controls upon Kaveri River drainage, cratonic Peninsular India: Inferences from longitudinal profiles, morphotectonic indices, hanging valleys and fluvial records

NASA Astrophysics Data System (ADS)

Kale, Vishwas S.; Sengupta, Somasis; Achyuthan, Hema; Jaiswal, Manoj K.

2014-12-01

The Indian Peninsula is generally considered as a tectonically stable region, where ancient rocks, rivers and land surfaces predominate. In some parts of this ancient landscape, however, the role of tectonic landsculpting is strongly indicated by the presence of youthful topography and historical seismic activity. The present study is primarily focused on the middle domain of the Kaveri River, which displays such youthful features. The tectonic controls on this cratonic river were evaluated on the basis of the investigations of the longitudinal profiles, morphotectonic indices of active tectonics, and fluvial records. The presence of steep channel gradients, prominent knickpoints, hanging valleys, narrow bedrock gorges, and channel-in-channel morphology imply rapid erosion rates in the middle domain of the basin in response to active deformation, particularly in the reach defined by two major active faults - the Kollegal-Sivasamudram Fault and the Mekedatu Fault. Further, considering the remarkably low modern and long-term denudation rates and OSL ages of the alluvial deposits (30-40 ka), the tectonically-driven rejuvenation does not appear to be geologically recent as postulated by earlier workers.
Drilling to investigate processes in active tectonics and magmatism

NASA Astrophysics Data System (ADS)

Shervais, J.; Evans, J.; Toy, V.; Kirkpatrick, J.; Clarke, A.; Eichelberger, J.

2014-12-01

Coordinated drilling efforts are an important method to investigate active tectonics and magmatic processes related to faults and volcanoes. The US National Science Foundation (NSF) recently sponsored a series of workshops to define the nature of future continental drilling efforts. As part of this series, we convened a workshop to explore how continental scientific drilling can be used to better understand active tectonic and magmatic processes. The workshop, held in Park City, Utah, in May 2013, was attended by 41 investigators from seven countries. Participants were asked to define compelling scientific justifications for examining problems that can be addressed by coordinated programs of continental scientific drilling and related site investigations. They were also asked to evaluate a wide range of proposed drilling projects, based on white papers submitted prior to the workshop. Participants working on faults and fault zone processes highlighted two overarching topics with exciting potential for future scientific drilling research: (1) the seismic cycle and (2) the mechanics and architecture of fault zones. Recommended projects target fundamental mechanical processes and controls on faulting, and range from induced earthquakes and earthquake initiation to investigations of detachment fault mechanics and fluid flow in fault zones. Participants working on active volcanism identified five themes: the volcano eruption cycle; eruption sustainability, near-field stresses, and system recovery; eruption hazards; verification of geophysical models; and interactions with other Earth systems. Recommended projects address problems that are transferrable to other volcanic systems, such as improved methods for identifying eruption history and constraining the rheological structure of shallow caldera regions. Participants working on chemical geodynamics identified four major themes: large igneous provinces (LIPs), ocean islands, continental hotspot tracks and rifts, and
Tectonic map of Uruguay

NASA Astrophysics Data System (ADS)

Sanchez Bettucci, L.; Oyhantcabal, P.

2008-05-01

A compilation of available data about the geology of Uruguay allowed the definition of its main events and tectonic units. Based on a critical revision of different tectonic hypothesis found in the literature, a parsimonious tectonic evolution schema is presented, in the context of Western Gondwana. The tectonic map illustrates the general features of the structure and main tectonic units of Uruguay. The Precambrian shield, cropping out in the South and Southeast of the country is an Archean to Paleoprtoerozoic basement divided in three main tectonostratigraphic terrranes: the Piedra Alta (PAT) a juvenile Paleoproterozoic unit not reworked by later events; the Nico Pérez (NPT) a complex unit composed of several blocks where Archean to Mesoproterozoic events are recognised. The NPT was strongly reworked by Neoproterozoic (Brasiliano) orogeny. The Dom Feliciano Belt cropping out in eastern Uruguay is related to Western Gondwana amalgamation. Different tectonic settings are considered: pre-Brasiliano Basement inliers; supracrustal successions representing the evolution from a back- arc to a foreland basin; a magmatic arc; and post-collisional basins and related magmatism. In lower Paleozoic the Paraná foreland basin was generated as a consequence of orogenic events. The sedimentary successions in Uruguay include continental to shallow marine deposits where the influence of carboniferous to Permian glacial episode is recorded. The Mesozoic record is characterised by the influence of extension related to the break-up of Gondwana and the formation of the Atlantic Ocean: huge amounts of tholeiitic basalt were erupted (near 30.000 km3 in Uruguay), followed by cretaceous sediments in the northern area of the country while in the south-east, bimodal magmatism and sediments of the same age are associated to rift basins. The Cenozoic is characterised by tectonic quiescence. Subsidence is only observed in the western region (Chaco-Paraná Basin) and in the east (Laguna Mer
Late Quaternary tectonic activity and lake level change in the Rukwa Rift Basin

NASA Astrophysics Data System (ADS)

Delvaux, D.; Kervyn, F.; Vittori, E.; Kajara, R. S. A.; Kilembe, E.

1998-04-01

Interpretation of remotely sensed images and air photographs, compilation of geological and topographical maps, morphostructural and fault kinematic observations and 14C dating reveal that, besides obvious climatic influences, the lake water extent and sedimentation in the closed hydrological system of Lake Rukwa is strongly influenced by tectonic processes. A series of sandy ridges, palaeolacustrine terraces and palaeounderwater delta fans are related to an Early Holocene high lake level and subsequent progressive lowering. The maximum lake level was controlled by the altitude of the watershed between the Rukwa and Tanganyika hydrological systems. Taking as reference the present elevation of the palaeolacustrine terraces around Lake Rukwa, two orders of vertical tectonic movement are evidenced: i) a general uplift centred on the Rungwe Volcanic Province between the Rukwa and Malawi Rift Basins; and ii) a tectonic northeastward tilting of the entire Rukwa Rift Basin, including the depression and rift shoulders. This is supported by the observed hydromorphological evolution. Local uplift is also induced by the development of an active fault zone in the central part of the depression, in a prolongation of the Mbeya Range-Galula Fault system. The Ufipa and Lupa Border Faults, bounding the Rukwa depression on the southwestern and northeastern sides, respectively, exert passive sedimentation control only. They appear inactive or at least less active in the Late Quaternary than during the previous rifting stage. The main Late Quaternary tectonic activity is represented by dextral strike-slip movement along the Mbeya Range-Galula Fault system, in the middle of the Rukwa Rift Basin, and by normal dip-slip movements along the Kanda Fault, in the western rift shoulder.
Cenozoic tectonic reorganizations of the Death Valley region, southeast California and southwest Nevada

USGS Publications Warehouse

Fridrich, Christopher J.; Thompson, Ren A.

2011-01-01

The Death Valley region, of southeast California and southwest Nevada, is distinct relative to adjacent regions in its structural style and resulting topography, as well as in the timing of basin-range extension. Cenozoic basin-fill strata, ranging in age from greater than or equal to 40 to approximately 2 million years are common within mountain-range uplifts in this region. The tectonic fragmentation and local uplift of these abandoned basin-fills indicate a multistage history of basin-range tectonism. Additionally, the oldest of these strata record an earlier, pre-basin-range interval of weak extension that formed broad shallow basins that trapped sediments, without forming basin-range topography. The Cenozoic basin-fill strata record distinct stratigraphic breaks that regionally cluster into tight age ranges, constrained by well-dated interbedded volcanic units. Many of these stratigraphic breaks are long recognized formation boundaries. Most are angular unconformities that coincide with abrupt changes in depositional environment. Deposits that bound these unconformities indicate they are weakly diachronous; they span about 1 to 2 million years and generally decrease in age to the west within individual basins and regionally, across basin boundaries. Across these unconformities, major changes are found in the distribution and provenance of basin-fill strata, and in patterns of internal facies. These features indicate rapid, regionally coordinated changes in strain patterns defined by major active basin-bounding faults, coincident with step-wise migrations of the belt of active basin-range tectonism. The regionally correlative unconformities thus record short intervals of radical tectonic change, here termed "tectonic reorganizations." The intervening, longer (about 3- to 5-million-year) interval of gradual, monotonic evolution in the locus and style of tectonism are called "tectonic stages." The belt of active tectonism in the Death Valley region has abruptly
Temporal Variation of Tectonic Tremor Activity Associated with Nearby Earthquakes

NASA Astrophysics Data System (ADS)

Chao, K.; Van der Lee, S.; Hsu, Y. J.; Pu, H. C.

2017-12-01

Tectonic tremor and slow slip events, located downdip from the seismogenic zone, hold the key to recurring patterns of typical earthquakes. Several findings of slow aseismic slip during the prenucletion processes of nearby earthquakes have provided new insight into the study of stress transform of slow earthquakes in fault zones prior to megathrust earthquakes. However, how tectonic tremor is associated with the occurrence of nearby earthquakes remains unclear. To enhance our understanding of the stress interaction between tremor and earthquakes, we developed an algorithm for the automatic detection and location of tectonic tremor in the collisional tectonic environment in Taiwan. Our analysis of a three-year data set indicates a short-term increase in the tremor rate starting at 19 days before the 2010 ML6.4 Jiashian main shock (Chao et al., JGR, 2017). Around the time when the tremor rate began to rise, one GPS station recorded a flip in its direction of motion. We hypothesize that tremor is driven by a slow-slip event that preceded the occurrence of the shallower nearby main shock, even though the inferred slip is too small to be observed by all GPS stations. To better quantify what the necessary condition for tremor to response to nearby earthquakes is, we obtained a 13-year ambient tremor catalog from 2004 to 2016 in the same region. We examine the spatiotemporal relationship between tremor and 37 ML>=5.0 (seven events with ML>=6.0) nearby earthquakes located within 0.5 degrees to the active tremor sources. The findings from this study can enhance our understanding of the interaction among tremor, slow slip, and nearby earthquakes in the high seismic hazard regions.
The tectonic puzzle of the Messina area (Southern Italy): Insights from new seismic reflection data

PubMed Central

Doglioni, Carlo; Ligi, Marco; Scrocca, Davide; Bigi, Sabina; Bortoluzzi, Giovanni; Carminati, Eugenio; Cuffaro, Marco; D'Oriano, Filippo; Forleo, Vittoria; Muccini, Filippo; Riguzzi, Federica

2012-01-01

The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side. PMID:23240075
The tectonic puzzle of the Messina area (Southern Italy): insights from new seismic reflection data.

PubMed

Doglioni, Carlo; Ligi, Marco; Scrocca, Davide; Bigi, Sabina; Bortoluzzi, Giovanni; Carminati, Eugenio; Cuffaro, Marco; D'Oriano, Filippo; Forleo, Vittoria; Muccini, Filippo; Riguzzi, Federica

2012-01-01

The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side.

Tectonic Processes on Europa: Tidal Stresses, Mechanical Response, and Visible Features

USGS Publications Warehouse

Greenberg, R.; Geissler, P.; Hoppa, G.; Tufts, B.R.; Durda, D.D.; Pappalardo, R.; Head, J.W.; Greeley, R.; Sullivan, R.; Carr, M.H.

1998-01-01

Europa's orbital eccentricity, driven by the resonance with Io and Ganymede, results in "diurnal" tides (3.5-day period) and possibly in nonsynchronous rotation. Both diurnal variation and nonsynchronous rotation can create significant stress fields on Europa's surface, and both effects may produce cracking. Patterns and time sequences of apparent tectonic features on Europa include lineaments that correlate with both sources of stress, if we take into account nonsynchronous rotation, after initial crack formation, by amounts ranging up to several tens of degrees. For example, the crosscutting time sequence of features in the Cadmus and Minos Linea region is consistent with a combined diurnal and nonsynchronous tensile-stress field, as it evolves during tens of degrees of nonsynchronous rotation. Constraints on the rotation rate from comparing Voyager and Galileo images show that significant rotation requires 104yr, but could be fast enough to have allowed significant rotation since the last global resurfacing, even if such resurfacing was as recent as a few million years ago. Once cracking is initiated, diurnal tides work cracks so that they open and close daily. Although the daily effect is small, over 105yr double ridges could plausibly be built along the cracks with sizes and morphologies consistent with observed structures, according to a model in which underlying liquid water fills the open cracks, partially freezes, and is extruded during the daily closing of the cracks. Thus, several lines of observational and theoretical evidence can be integrated if we assume nonsynchronous rotation and the existence of a liquid water layer. ?? 1998 Academic Press.
The Geomorphological Evolution of a Landscape in a Tectonically Active Region: the Sennwald Landslide

NASA Astrophysics Data System (ADS)

Aksay, Selçuk; Ivy-Ochs, Susan; Hippe, Kristina; Graemiger, Lorenz; Vockenhuber, Christof

2016-04-01

The Säntis nappe is a fold-and-thrust structure in eastern Switzerland consisting of numerous tectonic discontinuities that make rocks vulnerable to rock failure. The Sennwald landslide is one of those events that occurred due to the failure of Lower Cretaceous Helvetic limestones. This study reveals the surface exposure age of the event in relation to geological and tectonic setting, earthquake frequency of the Central Alps, and regional scale climate/weather influence. Our study comprises detailed mapping of landform features, thin section analysis of landslide boulder lithologies, landslide volume estimation, numerical DAN-3D run-out modelling, and the spatial and temporal relationship of the event. In the Sennwald landslide, 92 million m3 of limestones detached from the south-eastern wall of the Säntis nappe and slid with a maximum travel distance of ~4'500 m and a "fahrboeschung" angle of 15° along the SE-dipping sliding plane almost parallel to the orientation of the bedding plane. Numerical run-out modelling results match the extent and the thickness of landslide deposits as observed in the field. The original bedrock stratigraphy was preserved as geologically the top layer in the bedrock package travelled the farthest and the bottom layer came to rest closest to the release bedrock wall during the landslide. Velocities of maximum 90 m/s were obtained from the numerical run-out modelling. Total Cl and 36Cl were determined at ETH AMS facility with isotope dilution methods defined in the literature (Ivy-Ochs et al., 2004). Surface exposure ages of landslide deposits in the accumulation area are revealed from twelve boulders. The distribution of limestone boulders in the accumulation area, the exposure ages, and the numerical run-out modelling support the hypothesis that the Sennwald landslide was a single catastrophic event. The event is likely to have been triggered by at least light to moderate earthquakes (Mw=4.0-6.0). The historical and the last 40-year
Evaluating influence of active tectonics on spatial distribution pattern of floods along eastern Tamil Nadu, India

NASA Astrophysics Data System (ADS)

Selvakumar, R.; Ramasamy, SM.

2014-12-01

Flooding is a naturally recurrent phenomenon that causes severe damage to lives and property. Predictions on flood-prone zones are made based on intensity-duration of rainfall, carrying capacity of drainage, and natural or man-made obstructions. Particularly, the lower part of the drainage system and its adjacent geomorphic landforms like floodplains and deltaic plains are considered for analysis, but stagnation in parts of basins that are far away from major riverine systems is less unveiled. Similarly, uncharacteristic flooding in the upper and middle parts of drainage, especially in zones of an anomalous drainage pattern, is also least understood. Even though topographic differences are attributed for such anomalous spatial occurrence of floods, its genetic cause has to be identified for effective management practice. Added to structural and lithological variations, tectonic movements too impart micro-scale terrain undulations. Because active tectonic movements are slow-occurring, long-term geological processes, its resultant topographical variations and drainage anomalies are least correlated with floods. The recent floods of Tamil Nadu also exhibit a unique distribution pattern emphasizing the role of tectonics over it. Hence a detailed geoinformatics-based analysis was carried out to envisage the relationship between spatial distribution of flood and active tectonic elements such as regional arches and deeps, block faults, and graben and drainage anomalies such as deflected drainage, compressed meander, and eyed drainages. The analysis reveals that micro-scale topographic highs and lows imparted by active tectonic movements and its further induced drainage anomalies have substantially controlled the distribution pattern of flood.
Similar Ring Structures on Mars and Tibetan Plateau confirm recent tectonism on Martian Northern polar region

NASA Astrophysics Data System (ADS)

Anglés, A.; Li, Y. L.

2017-10-01

The polar regions of Mars feature layered deposits, some of which exist as enclosed zoning structures. These deposits raised strong interest since their discovery and still remain one of the most controversial features on Mars. Zoning structures that are enclosed only appear in the Northern polar region, where the disappearance of water bodies may have left behind huge deposits of evaporate salts. The origin of the layered deposits has been widely debated. Here we propose that the enclosed nature of the zoning structures indicates the result of recent tectonism. We compared similar structures at an analogue site located in the western Qaidam Basin of Tibetan Plateau, a unique tectonic setting with abundant saline deposits. The enclosed structures, which we term Ring Structures, in both the analogue site and in the Northern polar region of Mars, were formed by uplift induced pressurization and buoyancy of salts as the result of recent tectonic activity.
Global Tectonics of Enceladus: Numerical Model

NASA Astrophysics Data System (ADS)

Czechowski, Leszek

2016-10-01

Introduction: Enceladus, a satellite of Saturn, is the smallest celestial body in the Solar System where volcanic and tectonic activities are observed. Every second, the mass of 200 kg is ejected into space from the South Polar Terrain (SPT) - [1]. The loss of matter from the body's interior should lead to global compression of the crust. Typical effects of compression are: thrust faults, folding and subduction. However, such forms are not dominant on Enceladus. We propose here special tectonic process that could explain this paradox. Our hypotheses states that the mass loss from SPT is the main driving mechanism of the following tectonic processes: subsidence of SPT, flow in the mantle and motion of adjacent tectonic plates. The hypotheses is presented in [2], [3] and[4].We suggest that the loss of the volatiles results in a void, an instability, and motion of solid matter to fill the void. The motion is presented at the Fig.1 and includes:Subsidence of the 'lithosphere' of SPT.Flow of the matter in the mantle.Motion of plates adjacent to SPT towards the active regionMethods and results: The numerical model of processes presented is developed. It is based on the equations of continuous media..If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is 0.05 mmyr-1. However, numerical calculations indicate that all three types of motion are usually important. The role of a given motion depends on the viscosity distribution. Generally, for most of the models the subsidence is 0.02 mmyr-1, but mantle flow and plates' motion also play a role in filling the void. The preliminary results of the numerical model indicate also that the velocity of adjacent plates could be 0.02 mmyr-1 for the Newtonian rheology.Note that in our model the reduction of the crust area is not a result of compression but it is a result of the plate sinking. Therefore the compressional surface features do not have to be dominant. The SPT does not have to be
Active Structures as Deduced from Geomorphic Features: A case in Hsinchu Area, northwestern Taiwan

NASA Astrophysics Data System (ADS)

Chen, Y.; Shyu, J.; Ota, Y.; Chen, W.; Hu, J.; Tsai, B.; Wang, Y.

2002-12-01

Hsinchu area is located in the northwestern Taiwan, the fold-and thrust belt created by arc-continent collision between Eurasian and Philippine. Since the collision event is still ongoing, the island is tectonically active and full of active faults. According to the historical records, some of the faults are seismically acting. In Hsinchuarea two active faults, the Hsinchu and Hsincheng, have been previously mapped. To evaluate the recent activities, we studied the related geomorphic features by using newly developed Digital Elevation Model (DEM), the aerial photos and field investigation. Geologically, both of the faults are coupled with a hanging wall anticline. The anticlines are recently active due to the deformation of the geomorphic surfaces. The Hsinchu fault system shows complicate corresponding scarps, distributed sub-parallel to the fault trace previously suggested by projection of subsurface geology. This is probably caused by its strike-slip component tearing the surrounding area along the main trace. The scarps associated with the Hsincheng fault system are rather simple and unique. It offsets a flight of terraces all the way down to recent flood plain, indicating its long lasting activity. One to two kilometers to east of main trace a back-thrust is found, showing coupled vertical surface offsets with the main fault. The striking discovery in this study is that the surface deformation is only distributed in the southern bank of Touchien river, also suddenly decreasing when crossing another tear fault system, which is originated from Hsincheng fault in the west and extending southeastward parallel to the Touchien river. The strike-slip fault system mentioned above not only bisects the Hsinchu fault, but also divides the Hsincheng fault into segments. The supporting evidence found in this study includes pressure ridges and depressions. As a whole, the study area is tectonically dominated by three active fault systems and two actively growing anticlines
Geomorphology of submerged river channels indicates Late Quaternary tectonic activity in the Gulf of Trieste, Northern Adriatic

NASA Astrophysics Data System (ADS)

Vrabec, M.; Slavec, P.; Poglajen, S.; Busetti, M.

2012-04-01

We use multibeam and parametric subbottom sonar data, complemented with multichannel and high-resolution single-channel seismic profiles, to investigate sea-bottom morphology and subbottom sediment structure in the south-eastern half of the Gulf of Trieste, northern Adriatic Sea. The study area comprises 180 km2 of predominantly flat seabed with the water depth from 20 to 25 m. Pre-Quaternary basement consists of Mesozoic-Paleogene carbonate platform unit, overlain by Eocene marls and sandstones, covered by up to 300 m thick Quaternary sediments of predominantly continental origin. The uppermost few meters of sediment consist of Holocene fine-grained marine deposits. Structurally, the investigated area belongs to the imbricated rim of the Adriatic microplate and is dissected by several NE-dipping low-angle thrusts with up to several kms of displacement. The thrusts are cut by younger NE-SW-trending steeply dipping faults with sinistral and/or normal offset, mapped onshore. The continuation of those faults into the offshore area is suggested by mismatch of thrust structures between parallel seismic profiles. Geodetic data on present-day tectonic activity is controversial. Whereas the Adriatic microplate is currently moving northwards towards Eurasia at the rate of 2-4 mm/yr, the GNSS data show no measurable deformation in the Gulf of Trieste. On the other hand, onshore precise-levelling data suggest localized vertical motions in the range of 1 mm/yr, interpreted as an indication of thrust activity. High-resolution swath bathymetry revealed several current-related erosional and depositional features such as gullies and megadunes with up to 5 m of relief. The most conspicuous seabed morphological features are pre-Holocene river channels preserved in low-erosion submarine environment, which make excellent markers for studying the long-term geomorphological evolution of the area. The WNW-ESE-trending paleo-Rižana river is characterized by highly sinuous meandering
Mare Orientale: Widely Accepted Large Impact or a Regular Tectonic Depression?

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

2018-04-01

Mare Orientale is one of the critical features on Moon surface explaining its tectonics. The impact origin of it is widely accepted, but an attentive examination shows that this large Mare is a part of endogenous tectonic structure, not a random impact.
Lunar seismicity and tectonics

NASA Technical Reports Server (NTRS)

Lammlein, D. R.

1977-01-01

Results are presented for an analysis of all moonquake data obtained by the Apollo seismic stations during the period from November 1969 to May 1974 and a preliminary analysis of critical data obtained in the interval from May 1974 to May 1975. More accurate locations are found for previously located moonquakes, and additional sources are located. Consideration is given to the sources of natural seismic signals, lunar seismic activity, moonquake periodicities, tidal periodicities in moonquake activity, hypocentral locations and occurrence characteristics of deep and shallow moonquakes, lunar tidal control over moonquakes, lunar tectonism, the locations of moonquake belts, and the dynamics of the lunar interior. It is concluded that: (1) moonquakes are distributed in several major belts of global extent that coincide with regions of the youngest and most intense volcanic and tectonic activity; (2) lunar tides control both the small quakes occurring at great depth and the larger quakes occurring near the surface; (3) the moon has a much thicker lithosphere than earth; (4) a single tectonic mechanism may account for all lunar seismic activity; and (5) lunar tidal stresses are an efficient triggering mechanism for moonquakes.
Late Neogene and Active Tectonics along the Northern Margin of the Central Anatolian Plateau,TURKEY

NASA Astrophysics Data System (ADS)

Yildirim, C.; Schildgen, T. F.; Melnick, D.; Echtler, H. P.; Strecker, M. R.

2009-12-01

Margins of orogenic plateaus are conspicuous geomorphic provinces that archive tectonic and climatic variations related to surface uplift. Their growth is associated with spatial and temporal variations of mode and rate of tectonics and surface processes. Those processes can be strongly linked to the evolution of margins and plateaus thorough time. As one of the major morpho-tectonic provinces of Turkey, the Central Pontides (coinciding with the northern margin of the Central Anatolian Plateau (CAP)) display a remarkable topography and present valuable geologic and geomorphic indicators to identify active tectonics. Morpho-tectonic analysis, geological cross-sections, seismic profiles, and geodetic analysis reveal continuous deformation characterized by brittle faults from Late Miocene to recent across the northern margin of the CAP. In the Sinop Peninsula and offshore in the southern Black Sea, pervasive faulting and folding and uplift of Late Miocene to Quaternary marine deposits is related to active margin tectonics of the offshore southern Black Sea thrust and the onshore Balifaki and Erikli faults. In the Kastamonu-Boyabat sedimentary basin, the Late Miocene to Quaternary continental equivalents are strongly deformed by the Ekinveren Fault. This vergent inverse and thrust fault with overstepping en echelon segments deforms not only Quaternary travertines and conglomerates, but also patterns of the Pleistocene to Holocene drainage systems. In the southern Kastamonu-Boyabat basin, an antithetic thrust fault of the Ekinveren Fault system deformed also Quaternary fluviatile terrace deposits. Farther south, a dextral transpressive splay of the North Anatolian Fault (NAF) deforms pediment surfaces and forms the northern flank of the Ilgaz active mountain range. The Ilgaz Range rises up to 2587 m.a.s.l and is delimited by active segments of the NAF.The Central Pontides are located at the apex of northward convex arc of the NAF. Geodetic analysis indicate a deviation
Active faulting Vs other surface displacing complex geomorphic phenomena. Case studies from a tectonically active area, Abruzzi Region, central Apennines, Italy

NASA Astrophysics Data System (ADS)

Lo Sardo, Lorenzo; Gori, Stefano; Falcucci, Emanuela; Saroli, Michele; Moro, Marco; Galadini, Fabrizio; Lancia, Michele; Fubelli, Giandomenico; Pezzo, Giuseppe

2016-04-01

How can be univocally inferred the genesis of a linear surface scarp as the result of an active and capable fault (FAC) in tectonically active regions? Or, conversely, how it is possible to exclude that a scarp is the result of a capable fault activation? Trying to unravel this open questions, we show two ambiguous case studies about the problem of the identification of active and capable faults in a tectonically active area just based on the presence of supposed fault scarps at surface. The selected cases are located in the area comprised between the Middle Aterno Valley Fault (MAVF) and the Campo Imperatore Plain (Abruzzi Region, central Apennines), nearby the epicentral area of the April 6th, 2009 L'Aquila earthquake. In particular, the two case studies analysed are located in a region characterized by a widespread Quaternary faults and by several linear scarps: the case studies of (i) Prata D'Ansidonia area and (ii) Santo Stefano di Sessanio area. To assess the origin and the state of activity of the investigated geomorphic features, we applied a classical geological and geomorphological approach, based on the analysis of the available literature, the interpretation of the aerial photographs, field surveying and classical paleoseismological approach, the latter consisting in digging excavations across the analysed scarps. These analysis were then integrated by morphometrical analyses. As for case (i), we focused on determining the geomorphic "meaning" of linear scarps carved onto fluvial-deltaic conglomerates (dated to the Early Pleistocene; Bertini and Bosi, 1993), up to 3 meters high and up to 1,5 km long, that border a narrow, elongated and flat-bottom depressions, filled by colluvial deposits. These features groove the paleo-landsurface of Valle Daria (Bosi and Bertini, 1970), wide landsurface located between Barisciano and Prata D'Ansidonia. Entwining paleoseismological trenching with geophysical analyses (GPR, ERT and microgravimetrical prospections), it
Tectonic evolution of the terrestrial planets.

PubMed

Head, J W; Solomon, S C

1981-07-03

The style and evolution of tectonics on the terrestrial planets differ substantially. The style is related to the thickness of the lithosphere and to whether the lithosphere is divided into distinct, mobile plates that can be recycled into the mantle, as on Earth, or is a single spherical shell, as on the moon, Mars, and Mercury. The evolution of a planetary lithosphere and the development of plate tectonics appear to be influenced by several factors, including planetary size, chemistry, and external and internal heat sources. Vertical tectonic movement due to lithospheric loading or uplift is similar on all of the terrestrial planets and is controlled by the local thickness and rheology of the lithosphere. The surface of Venus, although known only at low resolution, displays features both similar to those on Earth (mountain belts, high plateaus) and similar to those on the smaller planets (possible impact basins). Improved understanding of the tectonic evolution of Venus will permit an evaluation of the relative roles of planetary size and chemistry in determining evolutionary style.
Tectonics of the Easter plate

NASA Technical Reports Server (NTRS)

Engeln, J. F.; Stein, S.

1984-01-01

A new model for the Easter plate is presented in which rift propagation has resulted in the formation of a rigid plate between the propagating and dying ridges. The distribution of earthquakes, eleven new focal mechanisms, and existing bathymetric and magnetic data are used to describe the tectonics of this area. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion. The Easter plate may reflect the tectonics of rift propagation on a large scale, where rigid plate tectonics requires boundary reorientation. Simple schematic models to illustrate the general features and processes which occur at plates resulting from large-scale rift propagation are used.
Interaction between active tectonics, erosion and diapirism, a case study from Habble-Rud in Southern Central Alborz (Northern Iran)

NASA Astrophysics Data System (ADS)

Jaberi, Maryam; Ghassemi, Mohammad R.; Shayan, Siavosh; Yamani, Mojtaba; Zamanzadeh, Seyed Mohammad

2018-01-01

The Alborz mountain chain is a region of active deformation within the Arabia-Eurasia continental collision zone. The southern part of central Alborz Mountains, in the north of Iran, represents complex tectonics because it is located at the border of two developing continental sedimentary basins between southern central Alborz and Central Iran. An arid and semi-arid climate, a large extent of Quaternary sediments, rugged topography, salt domes and faults with historical seismicity influence the Habble-Rud River catchment. In the present research, a number of tectonic geomorphologic indices were extracted from satellite imagery and 10 m DEM (digital elevation model) data in order to identify relative tectonic activity within the basin. The indices include: stream length-gradient index (Sl), drainage basin asymmetry (Af), index of mountain front sinuosity (Smf), hypsometric integral (Hi), index of drainage basin shape (Bs), ratio of valley-floor width to valley height (Vf), and fault density (Fd). Due to the presence of heterogeneous indices for all sections of the catchment causing large extension of Habble-Rud (3260 km2), all of the variables such as extremely erodible formations, faults and folds and salt tectonics on the Southern part; were put into a matrix table. As a new approach, the variables were put into the SAW (simple additive model) model as one of MADM (multi-attribute decision-making models) techniques. The study area was divided into four regions according to the values of SAW. These classes include very high (%11), high (48.3%), moderate (34.7%), and low activity (3.4%). The result of the model suggests that the study area is located on a changing tectonic trend in central Alborz from NW-SE to NE-SW. The regions with high relative tectonic activity in HR catchment correspond to the active Garmsar and Sorkhe-Kalout faults and diapirs.
Geomorphology and Neogene tectonic evolution of the Palomares continental margin (Western Mediterranean)

NASA Astrophysics Data System (ADS)

Gómez de la Peña, Laura; Gràcia, Eulàlia; Muñoz, Araceli; Acosta, Juan; Gómez-Ballesteros, María; R. Ranero, César; Uchupi, Elazar

2016-10-01

The Palomares continental margin is located in the southeastern part of Spain. The margin main structure was formed during Miocene times, and it is currently part of the wide deformation zone characterizing the region between the Iberian and African plates, where no well-defined plate boundary occurs. The convergence between these two plates is here accommodated by several structures, including the left lateral strike-slip Palomares Fault. The region is characterized by sparse, low to moderate magnitude (Mw < 5.2) shallow instrumental earthquakes, although large historical events have also occurred. To understand the recent tectonic history of the margin we analyze new high-resolution multibeam bathymetry data and re-processed three multichannel seismic reflection profiles crossing the main structures. The analysis of seafloor morphology and associated subsurface structure provides new insights of the active tectonic features of the area. In contrast to other segments of the southeastern Iberian margin, the Palomares margin contains numerous large and comparatively closely spaced canyons with heads that reach near the coast. The margin relief is also characterized by the presence of three prominent igneous submarine ridges that include the Aguilas, Abubacer and Maimonides highs. Erosive processes evidenced by a number of scars, slope failures, gullies and canyon incisions shape the present-day relief of the Palomares margin. Seismic images reveal the deep structure distinguishing between Miocene structures related to the formation of the margin and currently active features, some of which may reactivate inherited structures. The structure of the margin started with an extensional phase accompanied by volcanic accretion during the Serravallian, followed by a compressional pulse that started during the Latemost Tortonian. Nowadays, tectonic activity offshore is subdued and limited to few, minor faults, in comparison with the activity recorded onshore. The deep Algero
Tectonic patterns and regional stresses near Venusian coronae

NASA Astrophysics Data System (ADS)

Cyr, K. E.; Melosh, H. J.

1993-04-01

A stress analysis of tectonic patterns near Venusian coronae is reported. Combined local corona stresses and uniform regional stresses are used to predict patterns of surface tectonic features. The patterns are compared to those of coronae on Magellan images to determine the regional stress and elastic lithospheric thickness about the coronae. Regional stresses of 0.1-0.6 kbar and elastic lithospheric thicknesses of 10 +/- 5 km are estimated for three specific coronae.
The curious history of Tethys as evidenced by irregular craters and variable tectonism

NASA Astrophysics Data System (ADS)

Ferguson, S. N.; Rhoden, A.; Nayak, M.; Asphaug, E. I.

2017-12-01

At first glance, the surface of Saturn's moon Tethys appears dominated by craters and its large canyon system, Ithaca Chasma. However, high-resolution Cassini imagery reveals a surface rife with curious geologic features, perhaps indicative of non-heliocentric impact populations and, potentially, a history of tectonic activity. We mapped three regions on Tethys to survey the diversity of features present on the surface, determine crater counts for each region, map and analyze fracture patterns, and identify constraints on the impactor populations. One study region is just south and west of the Odysseus impact basin (R1), and the other two regions sit slightly west of Ithaca Chasma (R2 and R3). The regions were imaged at average resolutions of 200m/pix, which is adequate to identify craters down to D=1km. Of 1200 total craters counted, we have identified 195 elliptical craters and 28 polygonal craters. Elliptical craters likely form from slow, oblique impacts, whereas polygonal craters are indicative of underlying tectonic structure. We identified 605 small craters, D=1-2km, across the three regions; we find that R1 has many more 1-10 km craters than R2 and R3. We also mapped 367 linear features. The median and range of orientations of the linear features vary across the regions. Despite their proximity, the orientations of lineations in R2 and R3 are not consistent with the orientation of Ithaca Chasma. This could be suggestive of different epochs of tectonic activity on Tethys. When compared with R2 and R3, R1 has more small craters, more lineations, and a preferred orientation of lineations that is distinct from the other two regions. Possible causes for a larger population of small craters in R1 include secondary craters from Odysseus and oblique impacts from debris ejected from Tethys' co-orbital moons, which should create many more 1km craters in R1 than the other regions. Due to the oblique impact angles predicted for incoming co-orbital debris, these impacts
Soil radon measurements as a potential tracer of tectonic and volcanic activity.

PubMed

Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

2016-04-15

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.
Soil radon measurements as a potential tracer of tectonic and volcanic activity

NASA Astrophysics Data System (ADS)

Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

2016-04-01

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.
Soil radon measurements as a potential tracer of tectonic and volcanic activity

PubMed Central

Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

2016-01-01

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

Active tectonics on Lanzarote (Canary Islands) from the analysis of CGPS data

NASA Astrophysics Data System (ADS)

Riccardi, Umberto; Arnoso, Jose; Benavent, María Teresa; Velez, Emilio; Tammaro, Umberto; González Montesinos, Fuensanta

2017-04-01

We report on the analysis of about three years of CGPS data collected on a small network consisting in five permanent stations, with the largest baseline up to 40 km, spread over Timanfaya National Park in Lanzarote Island. The GPS stations are operated by different institutions, as follows: CAME is co-operated by the Institute of Geosciences (CSIC-UCM), DiSTAR and the Geodesy Research Group of University Complutense of Madrid (GRG-UCM), while LACV is operated by (CSIC-UCM and GRG-UCM). Stations HRIA, TIAS, YAIZ, belong to GRAFCAN (Cartographical Service of the Government of Canary Islands). Lanzarote is the most Northeast and the oldest island of the Canarian Archipelago (Spain), which is located on a transitional zone, a passive margin, between oceanic and continental crust. Due to some peculiarities in geochemistry and geochronology of the rocks as well as tectonics, the origin of the archipelago from a hot spot is still debated. In fact, the most recent Holocenic volcanism is scattered over the islands and the last eruption was a submarine one, occurred in October 2011 at El Hierro Island. The last eruption in Lanzarote was a 7 years voluminous eruptive cycle, occurred during the 18th century. Historical seismicity registered in the region, is customarily attributed to diffuse tectonic activity. This study is intended to contributing to shed light on the active tectonics on Lanzarote island and to separate between local and regional strain fields. With the aid of Gamit 10.6 software, we compute from the GPS observations the "ionofree" linear combinations in order to obtain the positions of the stations in ITRF2008 frame using daily sessions, and IGS precise ephemeris. The frame referencing of the network is realized by eleven IGS GPS stations. Then through a Kalman filtering procedure, implemented in GLOBK software, we obtain the final daily solutions by constraining the fiducial GPS stations to their ITRF2008 coordinates. For a reliable strain field retrieval
Tectonic Plate Movement.

ERIC Educational Resources Information Center

Landalf, Helen

1998-01-01

Presents an activity that employs movement to enable students to understand concepts related to plate tectonics. Argues that movement brings topics to life in a concrete way and helps children retain knowledge. (DDR)
Complex Tectonism on Ganymede

NASA Technical Reports Server (NTRS)

1997-01-01

Complex tectonism is evident in these images of Ganymede's surface. The solid state imaging camera on NASA's Galileo spacecraft imaged this region as it passed Ganymede during its second orbit through the Jovian system. The 80 kilometer (50 mile) wide lens-shaped feature in the center of the image is located at 32 degrees latitude and 188 degrees longitude along the border of a region of ancient dark terrain known as Marius Regio, and is near an area of younger bright terrain named Nippur Sulcus. The tectonism that created the structures in the bright terrain nearby has strongly affected the local dark terrain to form unusual structures such as the one shown here. The lens-like appearance of this feature is probably due to shearing of the surface, where areas have slid past each other and also rotated slightly. Note that in several places in these images, especially around the border of the lens-shaped feature, bright ridges appear to turn into dark grooves. Analysis of the geologic structures in areas like this are helping scientists to understand the complex tectonic history of Ganymede.
North is to the top-left of the image, and the sun illuminates the surface from the southeast. The image covers an area about 63 kilometers (39 miles) by 120 kilometers (75 miles) across at a resolution of 188 meters (627 feet) per picture element. The images were taken on September 6, 1996 at a range of 18,522 kilometers (11,576 miles) by the solid state imaging (CCD) system on NASA's Galileo spacecraft.
The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.
Tectonic signatures on active margins

NASA Astrophysics Data System (ADS)

Hogarth, Leah Jolynn

High-resolution Compressed High-Intensity Radar Pulse (CHIRP) surveys offshore of La Jolla in southern California and the Eel River in northern California provide the opportunity to investigate the role of tectonics in the formation of stratigraphic architecture and margin morphology. Both study sites are characterized by shore-parallel tectonic deformation, which is largely observed in the structure of the prominent angular unconformity interpreted as the transgressive surface. Based on stratal geometry and acoustic character, we identify three sedimentary sequences offshore of La Jolla: an acoustically laminated estuarine unit deposited during early transgression, an infilling or "healing-phase" unit formed during the transgression, and an upper transparent unit. The estuarine unit is confined to the canyon edges in what may have been embayments during the last sea-level rise. The healing-phase unit appears to infill rough areas on the transgressive surface that may be related to relict fault structures. The upper transparent unit is largely controlled by long-wavelength tectonic deformation due to the Rose Canyon Fault. This unit is also characterized by a mid-shelf (˜40 m water depth) thickness high, which is likely a result of hydrodynamic forces and sediment grain size. On the Eel margin, we observe three distinct facies: a seaward-thinning unit truncated by the transgressive surface, a healing-phase unit confined to the edges of a broad structural high, and a highly laminated upper unit. The seaward-thinning wedge of sediment below the transgressive surface is marked by a number of channels that we interpret as distributary channels based on their morphology. Regional divergence of the sequence boundary and transgressive surface with up to ˜8 m of sediment preserved across the interfluves suggests the formation of subaerial accommodation during the lowstand. The healing-phase, much like that in southern California, appears to infill rough areas in the
The Tectonics of Mercury: The View from Orbit

NASA Astrophysics Data System (ADS)

Watters, T. R.; Byrne, P. K.; Klimczak, C.; Enns, A. C.; Banks, M. E.; Walsh, L. S.; Ernst, C. M.; Robinson, M. S.; Gillis-Davis, J. J.; Solomon, S. C.; Strom, R. G.; Gwinner, K.

2011-12-01

Flybys of Mercury by the Mariner 10 and MESSENGER spacecraft revealed a broad distribution of contractional tectonic landforms, including lobate scarps, high-relief ridges, and wrinkle ridges. Among these, lobate scarps were seen as the dominant features and have been interpreted as having formed as a result of global contraction in response to interior cooling. Extensional troughs and graben, where identified, were generally confined to intermediate- to large-scale impact basins. However, the true global spatial distribution of tectonic landforms remained poorly defined because the flyby observations were limited in coverage and spatial resolution, and many flyby images were obtained under lighting geometries far from ideal for the detection and identification of morphologic features. With the successful insertion of MESSENGER into orbit in March 2011, we are exploiting the opportunity to characterize the tectonics of Mercury in unprecedented detail using images at high resolution and optimum lighting, together with topographic data obtained from Mercury Laser Altimeter (MLA) profiles and stereo imaging. We are digitizing all of Mercury's major tectonic landforms in a standard geographic information system format from controlled global monochrome mosaics (mean resolution 250 m/px), complemented by high-resolution targeted images (up to ~10 m/px), obtained by the Mercury Dual Imaging System (MDIS) cameras. On the basis of an explicit set of diagnostic criteria, we are mapping wrinkle ridges, high-relief ridges, lobate scarps, and extensional troughs and graben in separate shapefiles and cataloguing the segment endpoint positions, length, and orientation for each landform. The versatility of digital mapping facilitates the merging of this tectonic information with other MESSENGER-derived map products, e.g., volcanic units, surface color, geochemical variations, topography, and gravity. Results of this mapping work to date include the identification of extensional
Late cretaceous extensional tectonics and associated igneous activity on the northern margin of the Gulf of Mexico Basin

NASA Technical Reports Server (NTRS)

Bowen, R. L.; Sundeen, D. A.

1985-01-01

Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic activity involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern margin of the cratonic platform from Arkansas to Georgia.
Topography, surface properties, and tectonic evolution. [of Venus and comparison with earth

NASA Technical Reports Server (NTRS)

Mcgill, G. E.; Warner, J. L.; Malin, M. C.; Arvidson, R. E.; Eliason, E.; Nozette, S.; Reasenberg, R. D.

1983-01-01

Differences in atmospheric composition, atmospheric and lithospheric temperature, and perhaps mantle composition, suggest that the rock cycle on Venus is not similar to the earth's. While radar data are not consistent with a thick, widespread and porous regolith like that of the moon, wind-transported regolith could be cemented into sedimentary rock that would be indistinguishable from other rocks in radar returns. The elevation spectrum of Venus is strongly unimodal, in contrast to the earth. Most topographic features of Venus remain enigmatic. Two types of tectonic model are proposed: a lithosphere too thick or buoyant to participate in convective flow, and a lithosphere which, in participating in convective flow, implies the existence of plate tectonics. Features consistent with earth-like plate tectonics have not been recognized.
Geologic Map of the Snegurochka Planitia Quadrangle (V-1): Implications for Tectonic and Volcanic History of the North Polar Region of Venus

NASA Technical Reports Server (NTRS)

Hurwitz, D. M.; Head, J. W.

2009-01-01

Geologic mapping of Snegurochka Planitia (V-1) reveals a complex stratigraphy of tectonic and volcanic features that can provide insight into the geologic history of Venus and Archean Earth [1,2], including 1) episodes of both localized crustal uplift and mantle downwelling, 2) shifts from local to regional volcanic activity, and 3) a shift back to local volcanic activity. We present our progress in mapping the spatial and stratigraphic relationships of material units and our initial interpretations of the tectonic and volcanic history of the region surrounding the north pole of Venus
Tectonic Evolution of the Çayirhan Neogene Basin (Ankara), Central Turkey

NASA Astrophysics Data System (ADS)

Behzad, Bezhan; Koral, Hayrettin; İşb&idot; l, Duygu; Karaaǧa; ç, Serdal

2016-04-01

Çayırhan (Ankara) is located at crossroads of the Western Anatolian extensional region, analogous to the Basin and Range Province, and suture zone of the Neotethys-Ocean, which is locus of the North Anatolian Transform since the Late Miocene. To the north of Çayırhan (Ankara), a Neogene sedimentary basin comprises Lower-Middle Miocene and Upper Miocene age formations, characterized by swamp, fluvial and lacustrine settings respectively. This sequence is folded and transected by neotectonic faults. The Sekli thrust fault is older than the Lower-Middle Miocene age formations. The Davutoǧlan fault is younger than the Lower-Middle Miocene formations and is contemporaneous to the Upper Miocene formation. The Çatalkaya fault is younger than the Upper Miocene formation. The sedimentary and tectonic features provide information on mode, timing and evolution of this Neogene age sedimentary basin in Central Turkey. It is concluded that the region underwent a period of uplift and erosion under the influence of contractional tectonics prior to the Early-Middle Miocene, before becoming a semi-closed basin under influence of transtensional tectonics during the Early-Middle Miocene and under influence of predominantly extensional tectonics during the post-Late Miocene times. Keywords: Tectonics, Extension, Transtension, Stratigraphy, Neotectonic features.
Philippine microplate tectonics and hydrocarbon exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallagher, J.J. Jr.

1986-07-01

Hydrocarbon traps in the Philippine Islands developed during a long, complex history of microplate tectonics. Carbonate and clastic stratigraphic traps formed during Mesozoic and early Cenozoic rifting and drifting. Hydrocarbons, generated in deep rift basins, migrated to the traps during drifting. Later Cenozoic compressional tectonic activity and concomitant faulting enhanced some traps and destroyed others. Seismic data offshore from Palawan Island reveal the early trap histories. Later trap histories can be interpreted from seismic, outcrop, and remote-sensing data. Understanding the microplate tectonic history of the Philippines is the key to interpreting trap histories.
Tectonically Induced Anomalies Without Large Earthquake Occurrences

NASA Astrophysics Data System (ADS)

Shi, Zheming; Wang, Guangcai; Liu, Chenglong; Che, Yongtai

2017-06-01

In this study, we documented a case involving large-scale macroscopic anomalies in the Xichang area, southwestern Sichuan Province, China, from May to June of 2002, after which no major earthquake occurred. During our field survey in 2002, we found that the timing of the high-frequency occurrence of groundwater anomalies was in good agreement with those of animal anomalies. Spatially, the groundwater and animal anomalies were distributed along the Anninghe-Zemuhe fault zone. Furthermore, the groundwater level was elevated in the northwest part of the Zemuhe fault and depressed in the southeast part of the Zemuhe fault zone, with a border somewhere between Puge and Ningnan Counties. Combined with microscopic groundwater, geodetic and seismic activity data, we infer that the anomalies in the Xichang area were the result of increasing tectonic activity in the Sichuan-Yunnan block. In addition, groundwater data may be used as a good indicator of tectonic activity. This case tells us that there is no direct relationship between an earthquake and these anomalies. In most cases, the vast majority of the anomalies, including microscopic and macroscopic anomalies, are caused by tectonic activity. That is, these anomalies could occur under the effects of tectonic activity, but they do not necessarily relate to the occurrence of earthquakes.
Tectonics of the central Andes

NASA Technical Reports Server (NTRS)

Bloom, Arthur L.; Isacks, Bryan L.; Fielding, Eric J.; Fox, Andrew N.; Gubbels, Timothy L.

1989-01-01

Acquisition of nearly complete coverage of Thematic Mapper data for the central Andes between about 15 to 34 degrees S has stimulated a comprehensive and unprecedented study of the interaction of tectonics and climate in a young and actively developing major continental mountain belt. The current state of the synoptic mapping of key physiographic, tectonic, and climatic indicators of the dynamics of the mountain/climate system are briefly reviewed.
Plate tectonics of the Mediterranean region.

PubMed

McKenzie, D P

1970-04-18

The seismicity and fault plane solutions in the Mediterranean area show that two small rapidly moving plates exist in the Eastern Mediterranean, and such plates may be a common feature of contracting ocean basins. The results show that the concepts of plate tectonics apply to instantaneous motions across continental plate boundaries.
The contraction/expansion history of Charon with implications for its planetary-scale tectonic belt

NASA Astrophysics Data System (ADS)

Malamud, Uri; Perets, Hagai B.; Schubert, Gerald

2017-06-01

The New Horizons mission to the Kuiper belt has recently revealed intriguing features on the surface of Charon, including a network of chasmata, cutting across or around a series of high topography features, conjoining to form a belt. It is proposed that this tectonic belt is a consequence of contraction/expansion episodes in the moon's evolution associated particularly with compaction, differentiation and geochemical reactions of the interior. The proposed scenario involves no need for solidification of a vast subsurface ocean and/or a warm initial state. This scenario is based on a new, detailed thermo-physical evolution model of Charon that includes multiple processes. According to the model, Charon experiences two contraction/expansion episodes in its history that may provide the proper environment for the formation of the tectonic belt. This outcome remains qualitatively the same, for several different initial conditions and parameter variations. The precise orientation of Charon's tectonic belt, and the cryovolcanic features observed south of the tectonic belt may have involved a planetary-scale impact, that occurred only after the belt had already formed.
Magmatic tectonic effects of high thermal regime at the site of active ridge subduction: the Chile Triple Junction model

NASA Astrophysics Data System (ADS)

Lagabrielle, Yves; Guivel, Christèle; Maury, René C.; Bourgois, Jacques; Fourcade, Serge; Martin, Hervé

2000-11-01

High thermal gradients are expected to be found at sites of subduction of very young oceanic lithosphere and more particularly at ridge-trench-trench (RTT) triple junctions, where active oceanic spreading ridges enter a subduction zone. Active tectonics, associated with the emplacement of two main types of volcanic products, (1) MORB-type magmas, and (2) calc-alkaline acidic magmas in the forearc, also characterize these plate junction domains. In this context, MORB-type magmas are generally thought to derive from the buried active spreading center subducted at shallow depths, whereas the origin of calc-alkaline acidic magmas is more problematic. One of the best constrained examples of ridge-trench interaction is the Chile Triple Junction (CTJ) located southwest of the South American plate at 46°12'S, where the active Chile spreading center enters the subduction zone. In this area, there is a clear correlation between the emplacement of magmatic products and the migration of the triple junction along the active margin. The CTJ lava population is bimodal, with mafic to intermediate lavas (48-56% SiO 2) and acidic lavas ranging from dacites to rhyolites (66-73% SiO 2). Previous models have shown that partial melting of oceanic crust plus 10-20% of sediments, leaving an amphibole- and plagioclase-rich residue, is the only process that may account for the genesis of acidic magmas. Due to special plate geometry in the CTJ area, a given section of the margin may be successively affected by the passage of several ridge segments. We emphasize that repeated passages will lead to the development of very high thermal gradients allowing melting of rocks of oceanic origin at temperatures of 800-900°C and low pressures, corresponding to depths of 10-20 km depth only. In addition, the structure of the CTJ forearc domain is dominated by horizontal displacements and tilting of crustal blocks along a network of strike-slip faults. The occurrence of such a deformed domain implies
Tectonic tremor activity associated with teleseismic and nearby earthquakes

NASA Astrophysics Data System (ADS)

Chao, K.; Obara, K.; Peng, Z.; Pu, H. C.; Frank, W.; Prieto, G. A.; Wech, A.; Hsu, Y. J.; Yu, C.; Van der Lee, S.; Apley, D. W.

2016-12-01

Tectonic tremor is an extremely stress-sensitive seismic phenomenon located in the brittle-ductile transition section of a fault. To better understand the stress interaction between tremor and earthquake, we conduct the following studies: (1) search for triggered tremor globally, (2) examine ambient tremor activities associated with distant earthquakes, and (3) quantify the temporal variation of ambient tremor activity before and after nearby earthquakes. First, we developed a Matlab toolbox to enhance the searching of triggered tremor globally. We have discovered new tremor sources in the inland faults in Kyushu, Kanto, and Hokkaido in Japan, southern Chile, Ecuador, and central Colombia in South America, and in South Italy. Our findings suggest that tremor is more common than previously believed and indicate the potential existence of ambient tremor in the triggered tremor active regions. Second, we adapt the statistical analysis to examine whether the long-term ambient tremor rate may affect by the dynamic stress of teleseismic earthquakes. We analyzed the data in Nankai, Hokkaido, Cascadia, and Taiwan. Our preliminary results did not show an apparent increase of ambient tremor rate after the passing of surface waves. Third, we quantify temporal changes in ambient tremor activity before and after the occurrence of local earthquakes under the southern Central Range of Taiwan with magnitudes of >=5.5 from 2004 to 2016. For a particular case, we found a temporal variation of tremor rate before and after the 2010/03/04 Mw6.3 earthquake, located about 20 km away from the active tremor source. The long-term increase in the tremor rate after the earthquake could have been caused by an increase in static stress following the mainshock. For comparison, clear evidence from seismic and GPS observations indicate a short-term increase in the tremor rate a few weeks before the mainshock. The increase in the tremor rate before the mainshock could correlate with stress changes
Geophysical survey reveals tectonic structures in the Amundsen Sea embayment, West Antarctica

USGS Publications Warehouse

Gohl, K.; Eagles, G.; Netzeband, G.; Grobys, J.W.G.; Parsiegla, N.; Schlüter, P.; Leinweber, V.; Larter, R.D.; Uenzelmann-Neben, G.; Udintsev, G.B.

2007-01-01

Island Bay (PIB) reveal the crustal thickness and some tectonic features. The Moho is 24-22 km deep on the shelf. NE-SW trending magnetic and gravity anomalies and the thin crust indicate a former rift zone that was active during or in the run-up to breakup between Chatham Rise and West Antarctica before or at 90 Ma. NW-SE trending gravity and magnetic anomalies, following a prolongation of Peacock Sound, indicate the extensional southern boundary to the Bellingshausen Plate which was active between 79 and 61 Ma.
Grabens on Io: Evidence for Extensional Tectonics

NASA Astrophysics Data System (ADS)

Hoogenboom, T.; Schenk, P.

2012-12-01

Io may well be the most geologically active body in the solar system. A variety of volcanic features have been identified, including a few fissure eruptions, but tectonism is generally assumed to be limited to compression driven mountain formation (Schenk et al., 2001). A wide range of structural features can also be identified including scarps, lineaments, faults, and circular depressions (pits and patera rims). Narrow curvilinear graben (elongated, relatively depressed crustal unit or block that is bounded by faults on its sides) are also scattered across Io's volcanic plains. These features are dwarfed by the more prominent neighboring volcanoes and mountains, and have been largely ignored in the literature. Although they are likely to be extensional in origin, their relationship to local or global stress fields is unknown. We have mapped the locations, length and width of graben on Io using all available Voyager and Galileo images with a resolution better than 5 km. We compare the locations of graben with existing volcanic centers, paterae and mountain data to determine the degree of correlation between these geologic features and major topographic variations (basins/swells) in our global topographic map of Io (White et al., 2011). Graben are best observed in > 1-2 km low-sun angle images. Approximately 300 images were converted from ISIS to ArcMap format to allow easy comparison with the geological map of Io (Williams et al., 2012) along with previous higher resolution structural mapping of local areas (e.g. Crown et al., 1992). We have located >45 graben to date. Typically 1-3 kilometers across, some of these features can stretch for over 500 kilometers in length. Their formation may be related to global tidal stresses or local deformation. Io's orbit is eccentric and its solid surface experiences daily tides of up to ˜0.1 km, leading to repetitive surface strains of 10-4 or greater. These tides flex and stress the lithosphere and can cause it to fracture
Drainage - Structure Correlation in tectonically active Regions: Case studies in the Bolivian and Colombian Andes

NASA Astrophysics Data System (ADS)

Zeilinger, Gerold; Parra, Mauricio; Kober, Florian

2017-04-01

It is widely accepted, that drainage patterns are often controlled by tectonics/climate and geology/rheology. Classical drainage patterns can be found 1) in fault-and-thrust belt, where rives follow the valleys parallel or cut perpendicular to strike trough the ridges, forming a trellis pattern, 2) at dome structures where the drainage form a radial pattern or 3) rectangular patterns in strongly fractured regions. In this study, we focus on fault-and-thrust belts, that undergone different phases of tectonic activity. According to classical models, the deformation is propagating into the foreland, hence being youngest at the frontal part and getting successively older towards the axis of the orogen. Drainage patterns in the more interior parts of the orogenic wedge should be then less influenced by the direction of structures, as landscape evolution is changing to a tectonic passive stage. This relationship might represent the transience and maturity of drainage pattern evolution. Here we study drainage patterns of the Bolivian and the eastern Colombian Andes by comparing the relative orientation of the drainage network with the orogen structural grain. The drainage is extracted from Digital Elevation Models (SRTM 30 m) and indexed by their Strahler Order. Order 1 channels have an upstream area of 1 km2. The direction of all segments is analyzed by linear directional mean function that results in the mean orientation of input channels with approx. 500 m average length. The orientation of structures for different structural domains is calculated using the same function on digitized faults and fold-axis. Rose diagrams show the length-weighted directional distribution of structures, of higher (>= 4) and of lower order (<= 3) channels. The structural trend in the Bolivian Andes is controlled by the orocline, where a predominant NW-SE trend turns into an N-S trend at 18°S and where the eastern orogen comprise from west to east, the Eastern Cordillera (EC), the
Late Pleistocene-Holocene Activity of the Strike-slip Xianshuihe Fault Zone, Tibetan Plateau, Inferred from Tectonic Landforms

NASA Astrophysics Data System (ADS)

Lin, A.; Yan, B.

2017-12-01

Knowledges on the activity of the strike-slip fault zones on the Tibetan Plateau have been promoted greatly by the interpretation of remote sensing images (Molnar and Tapponnier, 1975; Tapponnier and Molnar, 1977). The active strike-slip Xianshuihe-Xiaojiang Fault System (XXFS), with the geometry of an arc projecting northeastwards, plays an important role in the crustal deformation of the Tibetan Plateau caused by the continental collision between the Indian and Eurasian plates. The Xianshuihe Fault Zone (XFZ) is located in the central segment of the XXFS and extends for 370 km, with a maximum sinistral offset of 60 km since 13‒5 Ma. In this study, we investigated the tectonic landforms and slip rate along the central segment of the left-lateral strike-slip XFZ. Field investigations and analysis of ttectonic landforms show that horizontal offset has been accumulated on the topographical markers of different scales that developed since the Last Glacial Maximum (LGM). The central segment of the XFZ is composed of three major faults: Yalahe, Selaha, and Zheduotang faults showing a right-stepping echelon pattern, that is characterized by systematical offset of drainages, alluvial fans and terrace risers with typical scissoring structures, indicating a structural feature of left-lateral strike-slip fault. Based on the offset glacial morphology and radiocarbon dating ages, we estimate the Late Pleistocene-Holocene slip rate to be 10 mm/yr for the central segment of the XFZ, which is consistent with that estimated from the GPS observations and geological evidence as reported previously. Across the central segment of the XFZ, the major Selaha and Zheduotang faults participate a slip rate of 5.8 mm/yr and 3.4 mm/yr, respectively. Detailed investigations of tectonic landforms are essential for the understanding the activity of active faults. Our findings suggest that the left-lateral slipping of the XFZ partitions the deformation of eastward extrusion and northeastward

Improve earthquake hypocenter using adaptive simulated annealing inversion in regional tectonic, volcano tectonic, and geothermal observation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ry, Rexha Verdhora, E-mail: rexha.vry@gmail.com; Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id

Observation of earthquakes is routinely used widely in tectonic activity observation, and also in local scale such as volcano tectonic and geothermal activity observation. It is necessary for determining the location of precise hypocenter which the process involves finding a hypocenter location that has minimum error between the observed and the calculated travel times. When solving this nonlinear inverse problem, simulated annealing inversion method can be applied to such global optimization problems, which the convergence of its solution is independent of the initial model. In this study, we developed own program codeby applying adaptive simulated annealing inversion in Matlab environment.more » We applied this method to determine earthquake hypocenter using several data cases which are regional tectonic, volcano tectonic, and geothermal field. The travel times were calculated using ray tracing shooting method. We then compared its results with the results using Geiger’s method to analyze its reliability. Our results show hypocenter location has smaller RMS error compared to the Geiger’s result that can be statistically associated with better solution. The hypocenter of earthquakes also well correlated with geological structure in the study area. Werecommend using adaptive simulated annealing inversion to relocate hypocenter location in purpose to get precise and accurate earthquake location.« less
Tectonic isolation from regional sediment sourcing of the Paradox Basin

NASA Astrophysics Data System (ADS)

Smith, T. M.; Saylor, J.; Sundell, K. E.; Lapen, T. J.

2017-12-01

feature among other intraplate, tectonically active basins.
Tectonic contrasts between Venus and the earth

NASA Technical Reports Server (NTRS)

Kaula, W. M.

1984-01-01

The long-wave features of the gravity field of Venus differ from those of the earth's field not only in their strong positive correlation with topography, but also in their gentler spectral slope. These properties are inconsistent with generation of the gravity field by plate tectonics or by processes at great depths; they are consistent with generation by a mantle convective system supporting the broad features in topography with an effective compensation depth of about 450 km.
Paleogeographic atlas project-Mesozoic-Cenozoic tectonic map of the world

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowley, D.B.; Ziegler, A.M.; Hulver, M.

1985-01-01

A Mesozoic-Cenozoic tectonic map of the world has been compiled in order to provide the basis for detailed paleogeographic, first-order palin-spastic and paleo-tectonic reconstructions. The map is plotted from a digital database on two polar stereographic projections that depict both time and type of tectonic activity. Time of activity is shown using six colors, with each color representing approximately 40 m.y. intervals. The time divisions correspond with, and are defined on the basis of times of major changes in plate motions. Tectonic activity is divided into 7 major types: (1) Platformal regions unaffected by major tectonism; (2) Region as underlainmore » by oceanic lithosphere; (3) Regions affected by extensional tectonism-characterized by thinning and stretching of the crust, including Atlantic-type margins, Basin and Range, back-arc and pull-apart basin development; (4) Regions of crustal shortening and thickening, as in collisional orogens and Andean-type foreland-fold systems; (5) Strike-slip systems associated with little or no change in crustal thickness; (6) Subduction accretion prisms, associated with tectonic outbuilding of continental crust, and marking sutures within continents; and (7) Large scale oceanic volcanic/magmatic arcs and plateaus characterized by increased crustal thickness and buoyancy of the lithosphere. The map provides a basis for understanding the assembly of Asia, the Circum-Pacific, and the disaggregation of Pangea.« less
Tectonics and volcanism on Mars: a compared remote sensing analysis with earthly geostructures

NASA Astrophysics Data System (ADS)

Baggio, Paolo; Ancona, M. A.; Callegari, I.; Pinori, S.; Vercellone, S.

1999-12-01

The recent knowledge on Mars' lithosphere evolution does not find yet sufficient analogies with the Earth's tectonic models. The Viking image analysis seems to be even now frequently, rather fragmentary, and do not permits to express any coherent relationships among the different detected phenomena. Therefore, today it is impossible to support any reliable kinematic hypothesis. The Remote-Sensing interpretation is addressed to a Viking image mosaic of the known Tharsis Montes region and particularly focused on the Arsia Mons volcano. Several previously unknown lineaments, not directly linked to volcano-tectonics, were detected. Their mutual relationships recall transcurrent kinematics that could be related to similar geostructural models known in the Earth plate tectonic dynamics. Several concordant relationships between the Arsia Mons volcano and the brittle extensive tectonic features of earthly Etnean district (Sicily, South Italy), interpreted on Landsat TM images, were pointed out. These analogies coupled with the recently confirmed strato- volcano topology of Tharsis Montes (Head and Wilson), the layout distribution of the effusive centers (Arsia, Pavonis and Ascraeus Montes), the new tectonic lineaments and the morphological features, suggest the hypothesis of a plate tectonic volcanic region. The frame could be an example in agreement with the most recent interpretation of Mars (Sleep). A buried circular body, previously incorrectly interpreted as a great landslide event from the western slope of Arsia Mons volcano, seems really to be a more ancient volcanic structure (Arsia Mons Senilis), which location is in evident relation with the interpreted new transcurrent tectonic system.
Paleoseismic and geomorphologic evidence of recent tectonic activity of the Pozohondo Fault (Betic Cordillera, SE Spain)

USGS Publications Warehouse

Rodríguez-Pascua, M.A.; Pérez-López, R.; Garduño-Monroy, V.H.; Giner-Robles, J.L.; Silva, P.G.; Perucha-Atienza, M.A.; Hernández-Madrigal, V.M.; Bischoff, J.

2012-01-01

Instrumental and historical seismicity in the Albacete province (External Prebetic Zone) has been scarcely recorded. However, major strike-slip faults showing NW-SE trending provide geomorphologic and paleoseismic evidence of recent tectonic activity (Late Pleistocene to Present). Moreover, these faults are consistently well oriented under the present stress tensor and therefore, they can trigger earthquakes of magnitude greater than M6, according to the lengths of surface ruptures and active segments recognized in fieldwork. Present landscape nearby the village of Hellin (SE of Albacete) is determined by the recent activity of the Pozohondo Fault (FPH), a NW-SE right-lateral fault with 90 km in length. In this study, we have calculated the Late Quaternary tectonic sliprate of the FPH from geomorphological, sedimentological, archaeoseimological, and paleoseismological approaches. All of these data suggest that the FPH runs with a minimum slip-rate of 0.1 mm/yr during the last 100 kyrs (Upper Pleistocene-Holocene). In addition, we have recognized the last two major paleoearthquakes associated to this fault. Magnitudes of these paleoearthquakes were gretarer than M6 and their recurrence intervals ranged from 6600 to 8600 yrs for the seismic cycle of FPH. The last earthquake was dated between the 1st and 6th centuries, though two earthquakes could be interpreted in this wide time interval, one at the FPH and other from a far field source. Results obtained here, suggest an increasing of the tectonic activity of the Pozohondo Fault during the last 10,000 yrs.
Early Miocene Tectonic Activity in the western Ross Sea (Antarctica)

NASA Astrophysics Data System (ADS)

Sauli, C.; Sorlien, C. C.; Busetti, M.; Geletti, R.; De Santis, L.

2012-12-01

In the framework of the Rossmap Italian PNRA work objectives to compile extended and revised digital maps of the main unconformities in Ross Sea, Antarctica, much additional seismic reflection data, that were not available to previous ANTOSTRAT compilation, were incorporated into a new ROSSMAP interpretation. The correlation across almost all of Ross Sea, from DSDP Site 270 and Site 272 in Eastern Basin to northern Victoria Land Basin, of additional early Miocene and late Oligocene horizons that were not part of ANTOSTRAT allows interpretations to be made of fault activity and glacial erosion or deposition at a finer time resolution. New conclusions include that extensional or transtensional fault activity within the zone between Victoria Land Basin and Northern Basin, initiated by 23 Ma or earlier, and continued after 18 Ma. Steep parallel-striking faults in southern Victoria Land Basin display both reverse and normal separation of 17.5 Ma (from Cape Roberts Program-core 1) and post-16 Ma horizons, suggesting an important strike-slip component. This result may be compared with published papers that proposed post-17 Ma extension in southern Victoria Land Basin, 16-17 Ma extension in the AdareTrough, north of the Ross Sea continental shelf, but no Miocene extension affecting the Northern Basin (Granot et al., 2010). Thus, our evidence for extension through the early Miocene is significant to post-spreading tectonic models. Reference Granot R., Cande S. C., Stock J. M., Davey F. J. and Clayton R. W. (2010) Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences. Geochem. Geophys. Geosyst., 8, Q08005, doi:10.1029/2010GC003105.
Glacier Ice Mass Fluctuations and Fault Instability in Tectonically Active Southern Alaska

NASA Technical Reports Server (NTRS)

SauberRosenberg, Jeanne M.; Molnia, Bruce F.

2003-01-01

Across southern Alaska the northwest directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. This has led to high tectonic strain rates and dramatic topographic relief of more than 5000 meters within 15 km of the Gulf of Alaska coast. The glaciers of this area are extensive and include large glaciers undergoing wastage (glacier retreat and thinning) and surges. The large glacier ice mass changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with ice mass fluctuations and tectonic loading by examining GPS geodetic observations and numerical model predictions. Although the glacial fluctuations perturb the tectonic stress field, especially at shallow depths, the largest contribution to ongoing crustal deformation is horizontal tectonic strain due to plate convergence. Tectonic forces are thus the primary force responsible for major earthquakes. However, for geodetic sites located < 10-20 km from major ice mass fluctuations, the changes of the solid Earth due to ice loading and unloading are an important aspect of interpreting geodetic results. The ice changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, ice mass fluctuations associated with the surge cycle can modify the short-term seismicity rates in a local region. For the thrust faulting environment of the study region a large decrease in ice load may cause an increase in seismic rate in a region close to failure whereas ice loading may inhibit thrust faulting.
Pit chains on Enceladus signal the recent tectonic dissection of the ancient cratered terrains

NASA Astrophysics Data System (ADS)

Martin, Emily S.; Kattenhorn, Simon A.; Collins, Geoffrey C.; Michaud, Robert L.; Pappalardo, Robert T.; Wyrick, Danielle Y.

2017-09-01

Enceladus is the first outer solar system body on which pit chains have been positively identified. We map the global distribution of pit chains and show that pit chains are among the youngest tectonic features on Enceladus's surface, concentrated in the cratered plains centered on Enceladus's Saturnian and anti-Saturnian hemispheres. Pit chains on Enceladus are interpreted as the surface expressions of subsurface dilational fractures underlying a cover of unconsolidated material, which we infer to be a geologically young cover of loose regolith that mantles the surface of Enceladus. A widespread layer of regolith may act to insulate the surface, which has implications for the thermal state of Enceladus's ice shell. The widespread distribution of pit chains across the cratered plains indicates that this ancient surface has recently been tectonically active.
This Dynamic Planet: World map of volcanoes, earthquakes, impact craters and plate tectonics

USGS Publications Warehouse

Simkin, Tom; Tilling, Robert I.; Vogt, Peter R.; Kirby, Stephen H.; Kimberly, Paul; Stewart, David B.

2006-01-01

Our Earth is a dynamic planet, as clearly illustrated on the main map by its topography, over 1500 volcanoes, 44,000 earthquakes, and 170 impact craters. These features largely reflect the movements of Earth's major tectonic plates and many smaller plates or fragments of plates (including microplates). Volcanic eruptions and earthquakes are awe-inspiring displays of the powerful forces of nature and can be extraordinarily destructive. On average, about 60 of Earth's 550 historically active volcanoes are in eruption each year. In 2004 alone, over 160 earthquakes were magnitude 6.0 or above, some of which caused casualties and substantial damage. This map shows many of the features that have shaped--and continue to change--our dynamic planet. Most new crust forms at ocean ridge crests, is carried slowly away by plate movement, and is ultimately recycled deep into the earth--causing earthquakes and volcanism along the boundaries between moving tectonic plates. Oceans are continually opening (e.g., Red Sea, Atlantic) or closing (e.g., Mediterranean). Because continental crust is thicker and less dense than thinner, younger oceanic crust, most does not sink deep enough to be recycled, and remains largely preserved on land. Consequently, most continental bedrock is far older than the oldest oceanic bedrock. (see back of map) The earthquakes and volcanoes that mark plate boundaries are clearly shown on this map, as are craters made by impacts of extraterrestrial objects that punctuate Earth's history, some causing catastrophic ecological changes. Over geologic time, continuing plate movements, together with relentless erosion and redeposition of material, mask or obliterate traces of earlier plate-tectonic or impact processes, making the older chapters of Earth's 4,500-million-year history increasingly difficult to read. The recent activity shown on this map provides only a present-day snapshot of Earth's long history, helping to illustrate how its present surface came to
Venus tectonics: initial analysis from magellan.

PubMed

Solomon, S C; Head, J W; Kaula, W M; McKenzie, D; Parsons, B; Phillips, R J; Schubert, G; Talwani, M

1991-04-12

Radar imaging and altimetry data from the Magellan mission have revealed a diversity of deformational features at a variety of spatial scales on the Venus surface. The plains record a superposition of different episodes of deformation and volcanism; strain is both areally distributed and concentrated into zones of extension and shortening. The common coherence of strain patterns over hundreds of kilometers implies that many features in the plains reflect a crustal response to mantle dynamic processes. Ridge belts and mountain belts represent successive degrees of lithospheric shortening and crustal thickening; the mountain belts also show widespread evidence for extension and collapse both during and following crustal compression. Venus displays two geometrical patterns of concentrated lithospheric extension: quasi-circular coronae and broad rises with linear rift zones; both are sites of significant volcanism. No long, large-offset strike-slip faults have been observed, although limited local horizontal shear is accommodated across many zones of crustal shortening. In general, tectonic features on Venus are unlike those in Earth's oceanic regions in that strain typically is distributed across broad zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on Earth.
Glacial reorganization of topography in a tectonically active mountain range

NASA Astrophysics Data System (ADS)

Adams, Byron; Ehlers, Todd

2016-04-01

Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns, and not tectonic rock uplift rates. Alpine glaciers drastically altered the relief structure of the Olympic Mountains. The details of these relief changes are recorded in channel profiles as overdeepenings, reduced slopes, and associated knickpoints. We find the position of these relief changes within the orogen is dependent on the position of the Pleistocene ELA. While alpine glaciers overdeepened valleys in regions near the Pleistocene ELA (which has a tendency to increase relief), headward erosion of west and north flowing glacier systems captured significant area from opposing systems and caused drainage divide lowering. This divide lowering reduced relief throughout the range. We demonstrate similar topographic effects recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on
Euramerican tonsteins: overview, magmatic origin, and depositional-tectonic implications

USGS Publications Warehouse

Lyons, P.C.; Spears, D.A.; Outerbridge, W.F.; Congdon, R.D.; Evans, H.T.

1994-01-01

Carboniferous tonsteins (kaolinized volcanic-ash beds) of wide geographic distribution are known in both Europe and North America. Relict volcanic minerals common in these Euramerican tonsteins are volcanic quartz (including beta-quartz paramorphs), zircon and ilmenite; less common are magnetite, fayalite, rutile, monazite, xenotime, apatite and sanidine. Data for two relatively thick (3-13 cm) and widespread (>400 km) European tonsteins (Erda and Sub-Worsley Four-foot) indicate an increase in detrital quartz near the top of the beds which indicates mixing with normal clastic sediments, including the introduction of heavy detrital minerals (e.g., tourmaline and garnet). These thick tonsteins show multiple horizontal bedding, normal graded bedding, disturbed bedding, and centimeter-scale scour surfaces. The Fire Clay tonstein in North America represents from one to five separate volcanic air-fall ash deposits as determined by normal graded bedding and mineralogical analysis. These features indicate several episodes of volcanic-ash deposition and very localized subsequent erosion and bioturbation. Electron microprobe data from glass inclusions in volcanic quartz in Euramerican tonsteins indicate a rhyolitic origin for these tonsteins and reveal chemical "fingerprints" valuable for intra- and inter-basinal correlations. However, the tectonic framework for European and North American tonsteins was quite different. In Europe, volcanic-ash beds were associated with Variscan collisional tectonics, whereas in North America, volcanic ash was associated with Ouachita tectonic activity, explosive volcanism from the Yucatan block, collision between the South American and North American plates, and the formation of Pangea. ?? 1994.
Late Cenozoic tectonic activity of the Altyn Tagh range: Constraints from sedimentary records from the Western Qaidam Basin, NE Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhang, Tao; Fang, Xiaomin; Wang, Yadong; Song, Chunhui; Zhang, Weilin; Yan, Maodu; Han, Wenxia; Zhang, Dawen

2018-07-01

The Altyn Tagh range (ATR) is the northern geological boundary of the Tibetan Plateau and plays a key role in accommodating its Cenozoic lithospheric deformation. However, knowledge of the structural style and age of uplift of the ATR is limited and controversial. The Qaidam Basin, in the southeast side of the ATR, provides an outstanding field laboratory for understanding the history and mechanisms of ATR growth. This study presents a detailed sedimentological analysis of a 1040-m-thick late Cenozoic ( 17-5.0 Ma) sedimentary sequence from the western Qaidam Basin, together with the analysis of sedimentological data from nearby boreholes and sections. Our aims were to determine the spatiotemporal evolution of the sedimentary sequences in the study area and to explore their response to late Cenozoic tectonic activity in the ATR. The results show three major intervals of the sedimentary characteristics in the study area: >17-16 Ma, 10 Ma and <5 Ma, which are closely related to the development of unconformities and growth strata recorded by high-resolution seismic reflection profiles. Combining the results with a comprehensive provenance analysis and with published records of regional climate change and tectonic activity, we discuss the possible factors responsible for the variations in the sedimentary characteristics of the studied sections. We conclude that significant tectonic responses in the western Qaidam Basin during the late Cenozoic were caused by three stages of tectonic activity of the ATR, at >17-16 Ma, 16-10 Ma and 10 Ma, during which the ATR respectively experienced tectonic uplift, fast strike-slip motion and intense uplift.
CHARACTER AND REGIONAL SIGNIFICANCE OF GREAT FALLS TECTONIC ZONE, EAST-CENTRAL IDAHO AND WEST-CENTRAL MONTANA.

USGS Publications Warehouse

O'Neill, J. Michael; Lopez, David A.

1985-01-01

The Great Falls tectonic zone, here named, is a belt of diverse northeast-trending geologic features that can be traced from the Idaho batholith in the Cordilleran miogeocline, across thrust-belt structures and basement rocks of west-central and southwestern Montana, through cratonic rocks of central Montana, and into southwestern-most Saskatchewan, Canada. Geologic mapping in east-central Idaho and west-central Montana has outlined a continuous zone of high-angle faults and shear zones. Recurrent fault movement in this zone and strong structural control over igneous intrusion suggest a fundamental tectonic feature that has influenced the tectonic development of the Idaho-Montana area from a least middle Proterozoic time to the present. Refs.
On the distinction of tectonic and nontectonic faulting in palaeoseismological research: a case study from the southern Marmara region of Turkey

NASA Astrophysics Data System (ADS)

Özaksoy, Volkan

2017-12-01

This study reports on spectacular deformation structures, including arrays of striated thrusts, discovered by excavation work in Holocene deposits in vicinity of a major neotectonic strike-slip fault in one of the tectonically most active regions of Turkey. The deformation structures were initially considered an evidence of sub-recent tectonic activity, but their detailed multidisciplinary study surprisingly revealed that the deformation of the clay-rich soil and its strongly weathered Jurassic substrate was of nontectonic origin, caused by argilliturbation. This phenomenon of vertisol self-deformation is well-known to pedologists, but may easily be mistaken for tectonic deformation by geologists less familiar with pedogenic processes. The possibility of argilliturbation thus needs to be taken into consideration in palaeoseismological field research wherever the deformed substrate consists of clay-rich muddy deposits. The paper reviews a range of specific diagnostic features that can serve as field criteria for the recognition of nontectonic deformation structures induced by argilliturbation in mud-dominated geological settings.
Channel morphometry, sediment transport, and implications for tectonic activity and surficial ages of Titan basins

USGS Publications Warehouse

Cartwright, R.; Clayton, J.A.; Kirk, R.L.

2011-01-01

Fluvial features on Titan and drainage basins on Earth are remarkably similar despite differences in gravity and surface composition. We determined network bifurcation (Rb) ratios for five Titan and three terrestrial analog basins. Tectonically-modified Earth basins have Rb values greater than the expected range (3.0-5.0) for dendritic networks; comparisons with Rb values determined for Titan basins, in conjunction with similarities in network patterns, suggest that portions of Titan's north polar region are modified by tectonic forces. Sufficient elevation data existed to calculate bed slope and potential fluvial sediment transport rates in at least one Titan basin, indicating that 75mm water ice grains (observed at the Huygens landing site) should be readily entrained given sufficient flow depths of liquid hydrocarbons. Volumetric sediment transport estimates suggest that ???6700-10,000 Titan years (???2.0-3.0??105 Earth years) are required to erode this basin to its minimum relief (assuming constant 1m and 1.5m flows); these lowering rates increase to ???27,000-41,000 Titan years (???8.0-12.0??105 Earth years) when flows in the north polar region are restricted to summer months. ?? 2011 Elsevier Inc.
Channel morphometry, sediment transport, and implications for tectonic activity and surficial ages of Titan basins

USGS Publications Warehouse

Cartwright, Richard; Clayton, Jordan A.; Kirk, Randolph L.

2011-01-01

Fluvial features on Titan and drainage basins on Earth are remarkably similar despite differences in gravity and surface composition. We determined network bifurcation (Rb) ratios for five Titan and three terrestrial analog basins. Tectonically-modified Earth basins have Rb values greater than the expected range (3.0–5.0) for dendritic networks; comparisons with Rb values determined for Titanbasins, in conjunction with similarities in network patterns, suggest that portions of Titan's north polar region are modified by tectonic forces. Sufficient elevation data existed to calculate bed slope and potential fluvial sedimenttransport rates in at least one Titanbasin, indicating that 75 mm water ice grains (observed at the Huygens landing site) should be readily entrained given sufficient flow depths of liquid hydrocarbons. Volumetric sedimenttransport estimates suggest that ~6700–10,000 Titan years (~2.0–3.0 x 105 Earth years) are required to erode this basin to its minimum relief (assuming constant 1 m and 1.5 m flows); these lowering rates increase to ~27,000–41,000 Titan years (~8.0–12.0 x 105 Earth years) when flows in the north polar region are restricted to summer months.
Architecture and evolution of an Early Permian carbonate complex on a tectonically active island in east-central California

USGS Publications Warehouse

Stevens, Calvin H.; Magginetti, Robert T.; Stone, Paul

2015-01-01

The newly named Upland Valley Limestone represents a carbonate complex that developed on and adjacent to a tectonically active island in east-central California during a brief interval of Early Permian (late Artinskian) time. This lithologically unique, relatively thin limestone unit lies within a thick sequence of predominantly siliciclastic rocks and is characterized by its high concentration of crinoidal debris, pronounced lateral changes in thickness and lithofacies, and a largely endemic fusulinid fauna. Most outcrops represent a carbonate platform and debris derived from it and shed downslope, but another group of outcrops represents one or possibly more isolated carbonate buildups that developed offshore from the platform. Tectonic activity in the area occurred before, probably during, and after deposition of this short-lived carbonate complex.
The QuakeSim Project: Numerical Simulations for Active Tectonic Processes

NASA Technical Reports Server (NTRS)

Donnellan, Andrea; Parker, Jay; Lyzenga, Greg; Granat, Robert; Fox, Geoffrey; Pierce, Marlon; Rundle, John; McLeod, Dennis; Grant, Lisa; Tullis, Terry

2004-01-01

In order to develop a solid earth science framework for understanding and studying of active tectonic and earthquake processes, this task develops simulation and analysis tools to study the physics of earthquakes using state-of-the art modeling, data manipulation, and pattern recognition technologies. We develop clearly defined accessible data formats and code protocols as inputs to the simulations. these are adapted to high-performance computers because the solid earth system is extremely complex and nonlinear resulting in computationally intensive problems with millions of unknowns. With these tools it will be possible to construct the more complex models and simulations necessary to develop hazard assessment systems critical for reducing future losses from major earthquakes.

Tectonic map of the Circum-Pacific region, Pacific basin sheet

USGS Publications Warehouse

Scheibner, E.; Moore, G.W.; Drummond, K.J.; Dalziel, Corvalan Q.J.; Moritani, T.; Teraoka, Y.; Sato, T.; Craddock, C.

2013-01-01

Circum-Pacific Map Project: The Circum-Pacific Map Project was a cooperative international effort designed to show the relationship of known energy and mineral resources to the major geologic features of the Pacific basin and surrounding continental areas. Available geologic, mineral, and energy-resource data are being complemented by new, project-developed data sets such as magnetic lineations, seafloor mineral deposits, and seafloor sediment. Earth scientists representing some 180 organizations from more than 40 Pacific-region countries are involved in this work. Six overlapping equal-area regional maps at a scale of 1:10,000,000 form the cartographic base for the project: the four Circum-Pacific Quadrants (Northwest, Southwest, Southeast, and Northeast), and the Antarctic and Arctic Sheets. There is also a Pacific Basin Sheet at a scale of 1:17,000,000. The Base Map Series and the Geographic Series (published from 1977 to 1990), the Plate-Tectonic Series (published in 1981 and 1982), the Geodynamic Series (published in 1984 and 1985), and the Geologic Series (published from 1984 to 1989) all include six map sheets. Other thematic map series in preparation include Mineral-Resources, Energy-Resources and Tectonic Maps. Altogether, more than 50 map sheets are planned. The maps were prepared cooperatively by the Circum-Pacific Council for Energy and Mineral Resources and the U.S. Geological Survey and are available from the Branch of Distribution, U. S. Geological Survey, Box 25286, Federal Center, Denver, Colorado 80225, U.S.A. The Circum-Pacific Map Project is organized under six panels of geoscientists representing national earth-science organizations, universities, and natural-resource companies. The six panels correspond to the basic map areas. Current panel chairmen are Tomoyuki Moritani (Northwest Quadrant), R. Wally Johnson (Southwest Quadrant), Ian W.D. Dalziel (Antarctic Region), vacant. (Southeast Quadrant), Kenneth J. Drummond (Northeast Quadrant), and
Coseismic landslides reveal near-surface rock strength in a high-relief tectonically active setting

USGS Publications Warehouse

Gallen, Sean F.; Clark, Marin K.; Godt, Jonathan W.

2014-01-01

We present quantitative estimates of near-surface rock strength relevant to landscape evolution and landslide hazard assessment for 15 geologic map units of the Longmen Shan, China. Strength estimates are derived from a novel method that inverts earthquake peak ground acceleration models and coseismic landslide inventories to obtain material proper- ties and landslide thickness. Aggregate rock strength is determined by prescribing a friction angle of 30° and solving for effective cohesion. Effective cohesion ranges are from 70 kPa to 107 kPa for 15 geologic map units, and are approximately an order of magnitude less than typical laboratory measurements, probably because laboratory tests on hand-sized specimens do not incorporate the effects of heterogeneity and fracturing that likely control near-surface strength at the hillslope scale. We find that strength among the geologic map units studied varies by less than a factor of two. However, increased weakening of units with proximity to the range front, where precipitation and active fault density are the greatest, suggests that cli- matic and tectonic factors overwhelm lithologic differences in rock strength in this high-relief tectonically active setting.
Mantle structure and tectonic history of SE Asia

NASA Astrophysics Data System (ADS)

Hall, Robert; Spakman, Wim

2015-09-01

Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic P-wave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia and including Malaysia, parts of the Philippines, New Guinea and northern Australia. We begin with an explanation of seismic tomography and causes of velocity anomalies in the mantle, and discuss assessment of model quality for tomographic models created from P-wave travel times. We then introduce the global P-wave velocity anomaly model UU-P07 and the tectonic model used in this paper and give an overview of previous interpretations of mantle structure. The slab-related velocity anomalies we identify in the upper and lower mantle based on the UU-P07 model are interpreted in terms of the tectonic model and illustrated with figures and movies. Finally, we discuss where tomographic and tectonic models for SE Asia converge or diverge, and identify the most important conclusions concerning the history of the region. The tomographic images of the mantle record subduction beneath the SE Asian region to depths of approximately 1600 km. In the upper mantle anomalies mainly record subduction during the last 10 to 25 Ma, depending on the region considered. We interpret a vertical slab tear crossing the entire upper mantle north of west Sumatra where there is a strong lateral kink in slab morphology, slab holes between c.200-400 km below East Java and Sumbawa, and offer a new three-slab explanation for subduction in the North Sulawesi region. There is a different structure in the lower mantle compared to the upper mantle and the deep structure changes from west to east. What was imaged in earlier models as a broad and deep anomaly below SE Asia has a clear internal structure and we argue that many features can be identified as older subduction zones. We identify remnants of slabs
Imaging different components of a tectonic tremor sequence in southwestern Japan using an automatic statistical detection and location method

NASA Astrophysics Data System (ADS)

Poiata, Natalia; Vilotte, Jean-Pierre; Bernard, Pascal; Satriano, Claudio; Obara, Kazushige

2018-06-01

the long-duration energy-release regions, matching the large-scale clustering features evidenced from the low-frequency earthquake's activity analysis. Further examination of the two catalogues showed that the extracted short-duration low-frequency earthquakes activity coincides in space, within about 10-15 km distance, with the longer-duration energy sources during the tectonic tremor sequence. This observation provides a potential constraint on the size of the longer-duration energy-radiating source region in relation with the clustering of low-frequency earthquakes activity during the analysed tectonic tremor sequence. We show that advanced statistical network-based methods offer new capabilities for automatic high-resolution detection, location and monitoring of different scale-components of tectonic tremor activity, enriching existing slow earthquakes catalogues. Systematic application of such methods to large continuous data sets will allow imaging the slow transient seismic energy-release activity at higher resolution, and therefore, provide new insights into the underlying multiscale mechanisms of slow earthquakes generation.
Imaging different components of a tectonic tremor sequence in southwestern Japan using an automatic statistical detection and location method

NASA Astrophysics Data System (ADS)

Poiata, Natalia; Vilotte, Jean-Pierre; Bernard, Pascal; Satriano, Claudio; Obara, Kazushige

2018-02-01

the long-duration energy-release regions, matching the large-scale clustering features evidenced from the low-frequency earthquake's activity analysis. Further examination of the two catalogues showed that the extracted short-duration low-frequency earthquakes activity coincides in space, within about 10-15 km distance, with the longer-duration energy sources during the tectonic tremor sequence. This observation provides a potential constraint on the size of the longer-duration energy-radiating source region in relation with the clustering of low-frequency earthquakes activity during the analysed tectonic tremor sequence. We show that advanced statistical network-based methods offer new capabilities for automatic high-resolution detection, location and monitoring of different scale-components of tectonic tremor activity, enriching existing slow earthquakes catalogues. Systematic application of such methods to large continuous data sets will allow imaging the slow transient seismic energy-release activity at higher resolution, and therefore, provide new insights into the underlying multi-scale mechanisms of slow earthquakes generation.
Discrimination and Assessment of Induced Seismicity in Active Tectonic Zones: A Case Study from Southern California

NASA Astrophysics Data System (ADS)

Bachmann, C. E.; Lindsey, N.; Foxall, W.; Robertson, M.

2014-12-01

Earthquakes induced by human activity have become a matter of heightened public concern during recent years. Of particular concern is seismicity associated with wastewater injection, which has included events having magnitudes greater than 5. The causes of the induced events are primarily changes in pore-pressure, fluid volume and perhaps temperature due to injection. Recent research in the US has focused on mid-continental regions having low rates of naturally-occurring seismicity, where induced events can be identified by relatively straightforward spatial and temporal correlation of seismicity with high-volume injection activities. Recent examples include events correlated with injection of wastewater in Oklahoma, Arkansas, Texas and Ohio, and long-term brine injection in the Paradox Valley in Colorado. Even in some of the cases where there appears at first sight to be a clear spatial correlation between seismicity and injection, it has been difficult to establish causality definitively. Here, we discuss methods to identify induced seismicity in active tectonic regions. We concentrate our study on Southern California, where large numbers of wastewater injection wells are located in oil-producing basins that experience moderate to high rates of naturally-occurring seismicity. Using the catalog of high-precision CISN relocations produced by Hauksson et al. (BSSA, 2012), we aim to discriminate induced from natural events based on spatio-temporal patterns of seismicity occurrence characteristics and their relationships to injection activities, known active faults and other faults favorably oriented for slip under the tectonic stress field. Since the vast majority of induced earthquakes are very small, it is crucial to include all events above the detection threshold of the CISN in each area studied. In addition to exploring the correlation of seismicity to injection activities in time and space, we analyze variations in frequency-magnitude distributions, which can
Lunar Tectonic Triad Joining Both Hemispheres and Its Terrestrial Analogue

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

2018-06-01

"Orbits make structures" — This three word notion explains similarities of fundamental tectonic features of the small satellite and much larger massive Earth. Very impressive are geoids of two bodies — similarity of SPA Basin and Indian depressions.
Tectonic Geomorphology.

ERIC Educational Resources Information Center

Bull, William B.

1984-01-01

Summarizes representative quantitative tectonic-geomorphology studies made during the last century, focusing on fault-bounded mountain-front escarpments, marine terraces, and alluvial geomorphic surfaces (considering stream terraces, piedmont fault scarps, and soils chronosequences). Also suggests where tectonic-geomorphology courses may best fit…
Teaching And Learning Tectonics With Web-GIS

NASA Astrophysics Data System (ADS)

Anastasio, D. J.; Sahagian, D. L.; Bodzin, A.; Teletzke, A. L.; Rutzmoser, S.; Cirucci, L.; Bressler, D.; Burrows, J. E.

2012-12-01

Tectonics is a new curriculum enhancement consisting of six Web GIS investigations designed to augment a traditional middle school Earth science curriculum. The investigations are aligned to Disciplinary Core Ideas: Earth and Space Science from the National Research Council's (2012) Framework for K-12 Science Education and to tectonics benchmark ideas articulated in the AAAS Project 2061 (2007) Atlas of Science Literacy. The curriculum emphasizes geospatial thinking and scientific inquiry and consists of the following modules: Geohazards, which plate boundary is closest to me? How do we recognize plate boundaries? How does thermal energy move around the Earth? What happens when plates diverge? What happens when plate move sideways past each other? What happens when plates collide? The Web GIS interface uses JavaScript for simplicity, intuition, and convenience for implementation on a variety of platforms making it easier for diverse middle school learners and their teachers to conduct authentic Earth science investigations, including multidisciplinary visualization, analysis, and synthesis of data. Instructional adaptations allow students who are English language learners, have disabilities, or are reluctant readers to perform advanced desktop GIS functions including spatial analysis, map visualization and query. The Web GIS interface integrates graphics, multimedia, and animation in addition to newly developed features, which allow users to explore and discover geospatial patterns that would not be easily visible using typical classroom instructional materials. The Tectonics curriculum uses a spatial learning design model that incorporates a related set of frameworks and design principles. The framework builds on the work of other successful technology-integrated curriculum projects and includes, alignment of materials and assessments with learning goals, casting key ideas in real-world problems, engaging students in scientific practices that foster the use of key
Martian plate tectonics

NASA Astrophysics Data System (ADS)

Sleep, N. H.

1994-03-01

The northern lowlands of Mars have been produced by plate tectonics. Preexisting old thick highland crust was subducted, while seafloor spreading produced thin lowland crust during late Noachian and Early Hesperian time. In the preferred reconstruction, a breakup margin extended north of Cimmeria Terra between Daedalia Planum and Isidis Planitia where the highland-lowland transition is relatively simple. South dipping subduction occured beneath Arabia Terra and east dipping subduction beneath Tharsis Montes and Tempe Terra. Lineations associated with Gordii Dorsum are attributed to ridge-parallel structures, while Phelegra Montes and Scandia Colles are interpreted as transfer-parallel structures or ridge-fault-fault triple junction tracks. Other than for these few features, there is little topographic roughness in the lowlands. Seafloor spreading, if it occurred, must have been relatively rapid. Quantitative estimates of spreading rate are obtained by considering the physics of seafloor spreading in the lower (approx. 0.4 g) gravity of Mars, the absence of vertical scarps from age differences across fracture zones, and the smooth axial topography. Crustal thickness at a given potential temperature in the mantle source region scales inversely with gravity. Thus, the velocity of the rough-smooth transition for axial topography also scales inversely with gravity. Plate reorganizations where young crust becomes difficult to subduct are another constraint on spreading age. Plate tectonics, if it occurred, dominated the thermal and stress history of the planet. A geochemical implication is that the lower gravity of Mars allows deeper hydrothermal circulation through cracks and hence more hydration of oceanic crust so that more water is easily subducted than on the Earth. Age and structural relationships from photogeology as well as median wavelength gravity anomalies across the now dead breakup and subduction margins are the data most likely to test and modify hypotheses
Active tectonics of the northern Mojave Desert: The 2017 Desert Symposium field trip road log

USGS Publications Warehouse

Miller, David; Reynolds, R.E.; Phelps, Geoffrey; Honke, Jeff; Cyr, Andrew J.; Buesch, David C.; Schmidt, Kevin M.; Losson, G.

2017-01-01

The 2017 Desert Symposium field trip will highlight recent work by the U.S. Geological Survey geologists and geophysicists, who have been mapping young sediment and geomorphology associated with active tectonic features in the least well-known part of the eastern California Shear Zone (ECSZ). This area, stretching from Barstow eastward in a giant arc to end near the Granite Mountains on the south and the Avawatz Mountains on the north (Fig. 1-1), encompasses the two major structural components of the ECSZ—east-striking sinistral faults and northwest-striking dextral faults—as well as reverseoblique and normal-oblique faults that are associated with topographic highs and sags, respectively. In addition, folds and stepovers (both restraining stepovers that form pop-up structures and releasing stepovers that create narrow basins) have been identified. The ECSZ is a segment in the ‘soft’ distributed deformation of the North American plate east of the San Andreas fault (Fig. 1-1), where it takes up approximately 20-25% of plate motion in a broad zone of right-lateral shear (Sauber et al., 1994) The ECSZ (sensu strictu) begins in the Joshua Tree area and passes north through the Mojave Desert, past the Owens Valley-to-Death Valley swath and northward, where it is termed the Walker Lane. It has been defined as the locus of active faulting (Dokka and Travis, 1990), but when the full history from about 10 Ma forward is considered, it lies in a broader zone of right shear that passes westward in the Mojave Desert to the San Andreas fault (Mojave strike-slip province of Miller and Yount, 2002) and passes eastward to the Nevada state line or beyond (Miller, this volume).We will visit several accessible highlights for newly studied faults, signs of young deformation, and packages of syntectonic sediments. These pieces of a complex active tectonic puzzle have yielded some answers to longstanding questions such as: How is fault slip transfer in this area accommodated
Quantitative study of tectonic geomorphology along Haiyuan fault based on airborne LiDAR

USGS Publications Warehouse

Chen, Tao; Zhang, Pei Zhen; Liu, Jing; Li, Chuan You; Ren, Zhi Kun; Hudnut, Kenneth W.

2014-01-01

High-precision and high-resolution topography are the fundamental data for active fault research. Light detection and ranging (LiDAR) presents a new approach to build detailed digital elevation models effectively. We take the Haiyuan fault in Gansu Province as an example of how LiDAR data may be used to improve the study of active faults and the risk assessment of related hazards. In the eastern segment of the Haiyuan fault, the Shaomayin site has been comprehensively investigated in previous research because of its exemplary tectonic topographic features. Based on unprecedented LiDAR data, the horizontal and vertical coseismic offsets at the Shaomayin site are described. The measured horizontal value is about 8.6 m, and the vertical value is about 0.8 m. Using prior dating ages sampled from the same location, we estimate the horizontal slip rate as 4.0 ± 1.0 mm/a with high confidence and define that the lower bound of the vertical slip rate is 0.4 ± 0.1 mm/a since the Holocene. LiDAR data can repeat the measurements of field work on quantifying offsets of tectonic landform features quite well. The offset landforms are visualized on an office computer workstation easily, and specialized software may be used to obtain displacement quantitatively. By combining precious chronological results, the fundamental link between fault activity and large earthquakes is better recognized, as well as the potential risk for future earthquake hazards.
Luminescence ages for alluvial-fan deposits in Southern Death Valley: Implications for climate-driven sedimentation along a tectonically active mountain front

USGS Publications Warehouse

Sohn, M.F.; Mahan, S.A.; Knott, J.R.; Bowman, D.D.

2007-01-01

Controversy exists over whether alluvial-fan sedimentation along tectonically active mountain fronts is driven by climatic changes or tectonics. Knowing the age of sedimentation is the key to understanding the relationship between sedimentation and its cause. Alluvial-fan deposits in Death Valley and throughout the arid southwestern United States have long been the subjects of study, but their ages have generally eluded researchers until recently. Most mapping efforts have recognized at least four major relative-age groupings (Q1 (oldest), Q2, Q3, and Q4 (youngest)), using observed changes in surface soils and morphology, relation to the drainage net, and development of desert pavement. Obtaining numerical age determinations for these morphologic stages has proven challenging. We report the first optically stimulated luminescence (OSL) ages for three of these four stages deposited within alluvial-fans along the tectonically active Black Mountains of Death Valley. Deposits showing distinct, remnant bar and swale topography (Q3b) have OSL ages from 7 to 4 ka., whereas those with moderate to poorly developed desert pavement and located farther above the active channel (Q3a) have OSL ages from 17 to 11 ka. Geomorphically older deposits with well-developed desert pavement (Q2d) have OSL ages ???25 ka. Using this OSL-based chronology, we note that alluvial-fan deposition along this tectonically active mountain front corresponds to both wet-to-dry and dry-to-wet climate changes recorded globally and regionally. These findings underscore the influence of climate change on alluvial fan deposition in arid and semi-arid regions. ?? 2007 Elsevier Ltd and INQUA.
Seismicity and active tectonics in the Alboran Sea, Western Mediterranean: Constraints from an offshore-onshore seismological network and swath bathymetry data

NASA Astrophysics Data System (ADS)

Grevemeyer, Ingo; Gràcia, Eulàlia; Villaseñor, Antonio; Leuchters, Wiebke; Watts, Anthony B.

2015-12-01

Seismicity and tectonic structure of the Alboran Sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in Spain and Morocco, an area where the convergence between the African and Eurasian plates causes distributed deformation. Crustal structure derived from local earthquake data suggests that the Alboran Sea is underlain by thinned continental crust with a mean thickness of about 20 km. During the 5 months of offshore network operation, a total of 229 local earthquakes were located within the Alboran Sea and neighboring areas. Earthquakes were generally crustal events, and in the offshore domain, most of them occurred at crustal levels of 2 to 15 km depth. Earthquakes in the Alboran Sea are poorly related to large-scale tectonic features and form a 20 to 40 km wide NNE-SSW trending belt of seismicity between Adra (Spain) and Al Hoceima (Morocco), supporting the case for a major left-lateral shear zone across the Alboran Sea. Such a shear zone is in accord with high-resolution bathymetric data and seismic reflection imaging, indicating a number of small active fault zones, some of which offset the seafloor, rather than supporting a well-defined discrete plate boundary fault. Moreover, a number of large faults known to be active as evidenced from bathymetry, seismic reflection, and paleoseismic data such as the Yusuf and Carboneras faults were seismically inactive. Earthquakes below the Western Alboran Basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere.
Evidence for Young Lunar Wrinkle Ridges: Ongoing Tectonic Activity on the Surface of the Moon?

NASA Astrophysics Data System (ADS)

Valantinas, A.; Kinch, K. M.

2017-12-01

The conventional understanding of the Moon states that it is a differentiated but currently a geologically `dead' body. Most of the lunar mare volcanism took place 4-3 Ga ago and basin related extensional tectonics ended 3.6 Ga ago [1]. There is evidence for much younger (0.9Ga -1.2 Ga) volcanic units [2,3] and some degree of contractional tectonics up to 1.2 Ga [4]. Other studies, however, identified evidence for ongoing tectonics based on narrow fractures and several young wrinkle ridges crossing the highlands and small craters [5]. In addition, there is evidence for young (<100 Ma) Irregular Mare Patches (IMPs) but their origin is still debated [6,7]. More recently high resolution images provided by NASA's Lunar Reconnaissance Orbiter revealed a number of surface tectonic expressions such as small graben and lobate scarps were found to be < 100 Ma [8,9]. In our work, we analyze several contractional lunar wrinkle ridge systems which are thought to be manifestations of global stress fields along nearside maria edges [10]. Stratigraphic relationships and the lack of large superimposing craters suggests that all wrinkle ridges in our study regions are Copernican. We derive model ages from crater size frequency distributions which result in ages all below 50 Ma. Analyzed lunar wrinkle ridges appear morphologically crisp and include various degrees of pristine rocky outcrops. High abundances of boulders suggest that they could be still tectonically active because meter size rock populations are obliterated by meteorite bombardment in 300 Ma [11,12]. [1] Basaltic Volcanism Study Project, Basaltic volcanism on the terrestrial planets, 948-974, 1981. [2] Schultz, P. H. & Spudis, P. D., Nature, 302, 184-186, 1983. [3] Hiesinger, H. et al., Geological Society of America Special Papers, 477, 2011.[4] Watters, T. R. & Johnson, C. L., Planetary Tectonics, 121-182, 2010. [5] Schultz, P. H., Moon Morphology, 1976. [6] Schultz, P. H. et al., Nature, 444, 184-186, 2006. [7
Tectonic state: its significance and characterization in the assessment of seismic effects associated with reservoir impounding

USGS Publications Warehouse

Castle, R.O.; Clark, M.M.; Grantz, A.; Savage, J.C.

1980-01-01

Any analysis of seismicity associated with the filling of large reservoirs requires an evaluation of the natural tectonic state in order to determine whether impoundment is the basic source, a mechanically unrelated companion feature, or a triggering stimulus of the observed seismicity. Several arguments indicate that the associated seismicity is usually a triggered effect. Among the elements of tectonic state considered here (existing fractures, accumulated elastic strain, and deformational style), deformational style is especially critical in forecasting the occurrence of impoundment-induced seismicity. The observational evidence indicates that seismicity associated with impounding generally occurs in areas that combine steeply dipping faults, relatively high strain rates, and either extensional or horizontal-shear strain. Simple physical arguments suggest: (1) that increased fluid pressures resulting from increased reservoir head should enhance the likelihood of seismic activity, whatever the tectonic environment; (2) that stress changes resulting from surface loading may increase the likelihood of crustal failure in areas of normal and transcurrent faulting, whereas they generally inhibit failure in areas of thrust faulting. Comparisons with other earthquake-producing artificial and natural processes (underground explosions, fluid injection, underground mining, fluid extraction, volcanic emissions) indicate that reservoir loading may similarly modify the natural tectonic state. Subsurface loading resulting from fluid extraction may be a particularly close analogue of reservoir loading; "seismotectonic" events associated with fluid extraction have been recognized in both seismically active and otherwise aseismic regions. Because the historic record of seismicity and surface faulting commonly is short in comparison with recurrence intervals of earthquake and fault-slip events, tectonic state is most reliably appraised through combined studies of historic
Quantitative morphometric analysis for the tectonic characterisation of northern Tunisia.

NASA Astrophysics Data System (ADS)

Camafort, Miquel; Pérez-Peña, José Vicente; Booth-Rea, Guillermo; Ranero, César R.; Gràcia, Eulàlia; Azañón, José Miguel; Melki, Fetheddine; Ouadday, Mohamed

2016-04-01

Northern Tunisia is characterized by low deformation rates and low to moderate seismicity. Although instrumental seismicity reaches maximum magnitudes of Mw 5.5, some historical earthquakes have occurred with catastrophic consequences in this region. Aiming to improve our knowledge of active tectonics in Tunisia, we carried out both a quantitative morphometric analysis and field study in the north-western region. We applied different morphometric tools, like river profiles, knickpoint analysis, hypsometric curves and integrals and drainage pattern anomalies in order to differentiate between zones with high or low recent tectonic activity. This analysis helps identifying uplift and subsidence zones, which we relate to fault activity. Several active faults in a sparse distribution were identified. A selected sector was studied with a field campaign to test the results obtained with the quantitative analysis. During the fieldwork we identified geological evidence of recent activity and a considerable seismogenic potential along El Alia-Teboursouk (ETF) and Dkhila (DF) faults. The ETF fault could be responsible of one of the most devastating historical earthquakes in northern Tunisia that destroyed Utique in 412 A.D. Geological evidence include fluvial terraces folded by faults, striated and cracked pebbles, clastic dikes, sand volcanoes, coseismic cracks, etc. Although not reflected in the instrumental seismicity, our results support an important seismic hazard, evidenced by the several active tectonic structures identified and the two seismogenic faults described. After obtaining the current active tectonic framework of Tunisia we discuss our results within the western Mediterranean trying to contribute to the understanding of the western Mediterranean tectonic context. With our results, we suggest that the main reason explaining the sparse and scarce seismicity of the area in contrast with the adjacent parts of the Nubia-Eurasia boundary is due to its extended
Climate dominated topography in a tectonically active mountain range

NASA Astrophysics Data System (ADS)

Adams, B. A.; Ehlers, T. A.

2015-12-01

Tests of the interactions between tectonic and climate forcing on Earth's topography often focus on the concept of steady-state whereby processes of rock deformation and erosion are opposing and equal. However, when conditions change such as the climate or tectonic rock uplift, then surface processes act to restore the balance between rock deformation and erosion by adjusting topography. Most examples of canonical steady-state mountain ranges lie within the northern hemisphere, which underwent a radical change in the Quaternary due to the onset of widespread glaciation. The activity of glaciers changed erosion rates and topography in many of these mountain ranges, which likely violates steady-state assumptions. With new topographic analysis, and existing patterns of climate and rock uplift, we explore a mountain range previously considered to be in steady-state, the Olympic Mountains, USA. The broad spatial trend in channel steepness values suggests that the locus of high rock uplift rates is coincident with the rugged range core, in a similar position as high temperature and pressure lithologies, but not in the low lying foothills as has been previously suggested by low-temperature thermochronometry. The details of our analysis suggest the dominant topographic signal in the Olympic Mountains is a spatial, and likely temporal, variation in erosional efficiency dictated by orographic precipitation, and Pleistocene glacier ELA patterns. We demonstrate the same topographic effects are recorded in the basin hypsometries of other Cenozoic mountain ranges around the world. The significant glacial overprint on topography makes the argument of mountain range steadiness untenable in significantly glaciated settings. Furthermore, our results suggest that most glaciated Cenozoic ranges are likely still in a mode of readjustment as fluvial systems change topography and erosion rates to equilibrate with rock uplift rates.
The Role of Geophysics in the New Global Tectonics

ERIC Educational Resources Information Center

Rudman, Albert J.

1969-01-01

Summarizes the developments in geophysics that have led to the concept of the new global tectonics, which attempts to explain such worldwide features as oceanic ridges and trenches, island arcs and young mountain chains, while it develops processes that cause earthquakes, volcanoes and major faulting. Evidence for the hypotheses of continental…
Simulation of active tectonic processes for a convecting mantle with moving continents

USGS Publications Warehouse

Trubitsyn, V.; Kaban, M.; Mooney, W.; Reigber, C.; Schwintzer, P.

2006-01-01

Numerical models are presented that simulate several active tectonic processes. These models include a continent that is thermally and mechanically coupled with viscous mantle flow. The assumption of rigid continents allows use of solid body equations to describe the continents' motion and to calculate their velocities. The starting point is a quasi-steady state model of mantle convection with temperature/ pressure-dependent viscosity. After placing a continent on top of the mantle, the convection pattern changes. The mantle flow subsequently passes through several stages, eventually resembling the mantle structure under present-day continents: (a) Extension tectonics and marginal basins form on boundary of a continent approaching to subduction zone, roll back of subduction takes place in front of moving continent; (b) The continent reaches the subduction zone, the extension regime at the continental edge is replaced by strong compression. The roll back of the subduction zone still continues after closure of the marginal basin and the continent moves towards the upwelling. As a result the ocean becomes non-symmetric and (c) The continent overrides the upwelling and subduction in its classical form stops. The third stage appears only in the upper mantle model with localized upwellings. ?? 2006 The Authors Journal compilation ?? 2006 RAS.

Distinguishing shocked from tectonically deformed quartz by the use of the SEM and chemical etching

USGS Publications Warehouse

Gratz, A.J.; Fisler, D.K.; Bohor, B.F.

1996-01-01

Multiple sets of crystallographically-oriented planar deformation features (PDFs) are generated by high-strain-rate shock waves at pressures of > 12 GPa in naturally shocked quartz samples. On surfaces, PDFs appear as narrow (50-500 nm) lamellae filled with amorphosed quartz (diaplectic glass) which can be etched with hydrofluoric acid or with hydrothermal alkaline solutions. In contrast, slow-strain-rate tectonic deformation pressure produces wider, semi-linear and widely spaced arrays of dislocation loops that are not glass filled. Etching samples with HF before examination in a scanning electron microscope (SEM) allows for unambiguous visual distinction between glass-filled PDFs and glass-free tectonic deformation arrays in quartz. This etching also reveals the internal 'pillaring' often characteristic of shock-induced PDFs. This technique is useful for easily distinguishing between shock and tectonic deformation in quartz, but does not replace optical techniques for characterizing the shock features.
Dating Tectonic Activity on Mercury’s Large-Scale Lobate-Scarp Thrust Faults

NASA Astrophysics Data System (ADS)

Barlow, Nadine G.; E Banks, Maria

2017-10-01

Mercury’s widespread large-scale lobate-scarp thrust faults reveal that the planet’s tectonic history has been dominated by global contraction, primarily due to cooling of its interior. Constraining the timing and duration of this contraction provides key insight into Mercury’s thermal and geologic evolution. We combine two techniques to enhance the statistical validity of size-frequency distribution crater analyses and constrain timing of the 1) earliest and 2) most recent detectable activity on several of Mercury’s largest lobate-scarp thrust faults. We use the sizes of craters directly transected by or superposed on the edge of the scarp face to define a count area around the scarp, a method we call the Modified Buffered Crater Counting Technique (MBCCT). We developed the MBCCT to avoid the issue of a near-zero scarp width since feature widths are included in area calculations of the commonly used Buffered Crater Counting Technique (BCCT). Since only craters directly intersecting the scarp face edge conclusively show evidence of crosscutting relations, we increase the number of craters in our analysis (and reduce uncertainties) by using the morphologic degradation state (i.e. relative age) of these intersecting craters to classify other similarly degraded craters within the count area (i.e., those with the same relative age) as superposing or transected. The resulting crater counts are divided into two categories: transected craters constrain the earliest possible activity and superposed craters constrain the most recent detectable activity. Absolute ages are computed for each population using the Marchi et al. [2009] model production function. A test of the Blossom lobate scarp indicates the MBCCT gives statistically equivalent results to the BCCT. We find that all scarps in this study crosscut surfaces Tolstojan or older in age (>~3.7 Ga). The most recent detectable activity along lobate-scarp thrust faults ranges from Calorian to Kuiperian (~3.7 Ga to
Active tectonics of the southeastern Upper Rhine Graben, Freiburg area (Germany)

NASA Astrophysics Data System (ADS)

Nivière, B.; Bruestle, A.; Bertrand, G.; Carretier, S.; Behrmann, J.; Gourry, J.-C.

2008-03-01

The Upper Rhine Graben has two Plio-Quaternary depocentres usually interpreted as resulting from tectonic reactivation. The southern basin, near Freiburg im Breisgau (Germany), contains up to 250 m of sediments. Beneath the younger alluvial deposits related to the current drainage system, a former river network deeply entrenched in the substratum reveals a very low regional base level of early Pleistocene age. The offset of channels at faults allows us to infer a Pleistocene reactivation of the syn-rift fault pattern and the estimation of slip rates. Maximum vertical movements along the faults have not exceeded 0.1 mm/yr since the middle Pleistocene. Current activity is concentrated along the westernmost faults. Morphologic markers indicate late Pleistocene reactivation of the Rhine River fault, and geophysical prospecting suggests a near-surface offset of young sedimentary deposits. The size of the fault segments potentially reactivated suggests that earthquakes with magnitude larger than Mw=6.3 could be expected in the area with a return interval of about 8000 years. Extrapolated to the duration of the Plio-Pleistocene, the strain rate estimates reveal that the tectonic forcing may account for only one-third to one-half of the whole thickness of the Plio-Pleistocene sediments of the basin fill. Thus other processes must be invoked to understand the growth of the Plio-Pleistocene basin. Especially the piracy of the Rhine River to the north during the early Pleistocene could explain these effects.
Why is understanding when Plate Tectonics began important for understanding Earth?

NASA Astrophysics Data System (ADS)

Korenaga, J.

2015-12-01

Almost all kinds of geological activities on Earth depend critically on the operation of plate tectonics, but did plate tectonics initiate right after the solidification of a putative magma ocean, or did it start much later, e.g., sometime during the Archean? This problem of the initiation of plate tectonics in the Earth history presents us a unique combination of observational and theoretical challenges. Finding geological evidence for the onset of plate tectonics is difficult because plate tectonics is a dynamic process that continuously destroys a remnant of the past. We therefore need to rely on more secondary traces, the interpretation of which often involves theoretical considerations. At the same time, it is still hard to predict, on a firm theoretical ground, when plate tectonics should have prevailed, because there is no consensus on why plate tectonics currently takes place on Earth. Knowing when plate tectonics began is one thing, and understanding why it did so is another. The initiation of plate tectonics is one of the last frontiers in earth science, which encourages a concerted effort from both geologists and geophysicists to identify key geological evidence and distinguish between competing theories of early Earth evolution. Such an endeavor is essential to arrive at a self-contained theory for the evolution of terrestrial planets.
Tectonics on Iapetus: Despinning, respinning, or something completely different?

NASA Astrophysics Data System (ADS)

Singer, Kelsi N.; McKinnon, William B.

2011-11-01

Saturn's moon Iapetus is unique in that it has apparently despun while retaining a substantial equatorial bulge. Stresses arising from such a non-hydrostatic shape should in principle cause surface deformation (tectonics). As part of a search for such a tectonic signature, lineaments (linear surface features) on Iapetus were mapped on both its bright and dark hemispheres. Lineament orientations were then compared to model stress patterns predicted for spin-down from a rotation period of 16.5 h (or less) to its present synchronous period, and for a range of lithospheric thicknesses. Many lineaments are straight segments of crater rimwalls, which may be faults or joints reactivated during complex crater collapse. Most striking are several large troughs on the bright, trailing hemisphere. These troughs appear to be extensional and are distinctive on that hemisphere, because the interior floors and walls of the troughs contain dark material. Globally, no specific evidence of strike slip or thrust offsets are seen, but this could be due to the age and degraded nature of any such features. We find that observed lineament orientations do not correlate with predicted patterns due to despinning on either hemisphere (the equatorial ridge was specifically excluded from this analysis, and is considered separately). Modest evidence for preferred orientations ±40° from north could be construed as consistent with respinning, which is not necessarily far-fetched. Assuming the rigidity of unfractured ice, predicted maximum lithospheric differential stresses from despinning range from ˜1 MPa to ˜160 MPa for the elastic spheroid and thin lithosphere limits, respectively (although it is only for thicker elastic lithospheres that we expect a nonhydrostatic state to be maintained over geologic time against lithospheric failure). The tectonic signature of despinning may have been obscured over time because the surface of Iapetus is very ancient, Iapetus' thick lithosphere may have
Temporal variation of tectonic tremor activity in southern Taiwan around the 2010 ML6.4 Jiashian earthquake

NASA Astrophysics Data System (ADS)

Chao, Kevin; Peng, Zhigang; Hsu, Ya-Ju; Obara, Kazushige; Wu, Chunquan; Ching, Kuo-En; van der Lee, Suzan; Pu, Hsin-Chieh; Leu, Peih-Lin; Wech, Aaron

2017-07-01

Deep tectonic tremor, which is extremely sensitive to small stress variations, could be used to monitor fault zone processes during large earthquake cycles and aseismic processes before large earthquakes. In this study, we develop an algorithm for the automatic detection and location of tectonic tremor beneath the southern Central Range of Taiwan and examine the spatiotemporal relationship between tremor and the 4 March 2010 ML6.4 Jiashian earthquake, located about 20 km from active tremor sources. We find that tremor in this region has a relatively short duration, short recurrence time, and no consistent correlation with surface GPS data. We find a short-term increase in the tremor rate 19 days before the Jiashian main shock, and around the time when the tremor rate began to rise one GPS station recorded a flip in its direction of motion. We hypothesize that tremor is driven by a slow-slip event that preceded the occurrence of the shallower Jiashian main shock, even though the inferred slip is too small to be observed by all GPS stations. Our study shows that tectonic tremor may reflect stress variation during the prenucleation process of a nearby earthquake.
Quaternary landscape evolution of tectonically active intermontane basins: the case of the Middle Aterno River Valley (Abruzzo, Central Italy)

NASA Astrophysics Data System (ADS)

Falcucci, Emanuela; Gori, Stefano; Della Seta, Marta; Fubelli, Giandomenico; Fredi, Paola

2014-05-01

The Middle Aterno River Valley is characterised by different Quaternary tectonic depressions localised along the present course of the Aterno River (Central Apennine) .This valley includes the L'Aquila and Paganica-Castelnuovo-San Demetrio tectonic basins, to the North, the Middle Aterno Valley and the Subequana tectonic basin, to the South. The aim of this contribution is to improve the knowledge about the Quaternary geomorphological and tectonic evolution of this portion of the Apennine chain. A synchronous lacustrine depositional phase is recognized in all these basins and attributed to the Early Pleistocene by Falcucci et al. (2012). At that time, this sector of the chain showed four distinct closed basins, hydrologically separated from each other and from the Sulmona depression. This depression, actually a tectonic basin too, was localized South of the Middle Aterno River Valley and it was drained by an endorheic hydrographic network. The formation of these basins was due to the activity of different fault systems, namely the Upper Aterno River Valley-Paganica system and San Pio delle Camere fault, to the North, and the Middle Aterno River Valley-Subequana Valley fault system to the South. These tectonic structures were responsible for the origin of local depocentres inside the depressions which hosted the lacustrine basins. Ongoing surveys in the uppermost sectors of the Middle Aterno River Valley revealed the presence of sub-horizontal erosional surfaces that are carved onto the carbonate bedrock and suspended several hundreds of metres over the present thalweg. Gently dipping slope breccias referred to the Early Pleistocene rest on these surfaces, thus suggesting the presence of an ancient low-gradient landscape adjusting to the local base level.. Subsequently, this ancient low relief landscape underwent a strong erosional phase during the Middle Pleistocene. This erosional phase is testified by the occurrence of valley entrenchment and of coeval fluvial
Wrench tectonics in Abu Dhabi, United Arab Emirates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrahim, M.; Mohamed, A.S.

1995-08-01

Recent studies of the geodynamics and tectonic history of the Arabian plate throughout geologic time have revealed that Wrench forces played an important role in the structural generation and deformation of Petroleum basins and reservoirs of the United Arab Emirates. The tectonic analysis of Abu Dhabi revealed that basin facies evolution were controlled by wrench tectonics, examples are the Pre-Cambrian salt basin, the Permo-Triassic and Jurassic basins. In addition, several sedimentary patterns were strongly influenced by wrench tectonics, the Lower Cretaceous Shuaiba platform margin and associated reservoirs is a good example. Wrench faults, difficult to identify by conventional methods, weremore » examined from a regional perspective and through careful observation and assessment of many factors. Subsurface structural mapping and geoseismic cross-sections supported by outcrop studies and geomorphological features revealed a network of strike slip faults in Abu Dhabi. Structural modelling of these wench forces including the use of strain ellipses was applied both on regional and local scales. This effort has helped in reinterpreting some structural settings, some oil fields were interpreted as En Echelon buckle folds associated with NE/SW dextral wrench faults. Several flower structures were interpreted along NW/SE sinistral wrench faults which have significant hydrocarbon potential. Synthetic and Antithetic strike slip faults and associated fracture systems have played a significant role in field development and reservoir management studies. Four field examples were discussed.« less
Role of tectonic inheritance in the instauration of Tunisian Atlassic fold-and-thrust belt: Case of Bouhedma - Boudouaou structures

NASA Astrophysics Data System (ADS)

Ghanmi, Mohamed Abdelhamid; Ghanmi, Mohamed; Aridhi, Sabri; Ben Salem, Mohamed Sadok; Zargouni, Fouad

2016-07-01

Tectonic inversion in the Bouhedma-Boudouaou Mountains was investigated through recent field work and seismic lines interpretation calibrated with petroleum well data. Located to the Central-Southern Atlas of Tunisia, this area signed shortened intra-continental fold-and-thrust belts. Two dissymmetric anticlines characterize Bouhedma - Boudouaou major fold. These structures show a strong virgation respectively from E-W to NNE-SSW as a response to the interference between both tectonic inversion and tectonic inheritance. This complex geometry is driven by Mesozoic rifting, which marked an extensional inherited regime. A set of late Triassic-Early Jurassic E-W and NW-SE normal faults dipping respectively to the North and to the East seems to widely affect the overall geodynamic evolution of this domain. They result in major thickness changes across the hanging wall and the footwall blocks in response with the rifting activity. Tectonic inversion is inferred from convergence between African and European plates since late Cretaceous. During Serravalian - Tortonian event, NW-SE trending paroxysm led to: 1) folding of pre-inversion and syn-inversion strata, 2) reactivation of pre-existing normal faults to reverse ones and 3) orogeny of the main structures with NE-SW and E-W trending. The compressional feature still remains active during Quaternary event (Post-Villafranchian) with N-S trending compression. Contraction during inversion generates folding and internal deformation as well as Fault-Propagation-Fold and folding related strike.
New constraints on the active tectonic deformation of the Aegean

USGS Publications Warehouse

Nyst, M.; Thatcher, W.

2004-01-01

revealed by seismicity, active faulting, fault geomorphology, and earthquake fault plane solutions, continental tectonics, at least in the Aegean, is to first order very similar to global plate tectonics and obeys the same simple kinematic rules. Although the widespread distribution of Aegean seismicity and active faulting might suggest a rather spatially homogeneous seismic hazard, the focusing of deformation near microplate boundaries implies the highest hazard is comparably localized.
The rotation and fracture history of Europa from modeling of tidal-tectonic processes

NASA Astrophysics Data System (ADS)

Rhoden, Alyssa Rose

Europa's surface displays a complex history of tectonic activity, much of which has been linked to tidal stress caused by Europa's eccentric orbit and possibly non-synchronous rotation of the ice shell. Cycloids are arcuate features thought to have formed in response to tidal normal stress while strike-slip motion along preexisting faults has been attributed to tidal shear stress. Tectonic features thus provide constraints on the rotational parameters that govern tidal stress, and can help us develop an understanding of the tidal-tectonic processes operating on ice covered ocean moons. In the first part of this work (Chapter 3), I test tidal models that include obliquity, fast precession, stress due to non-synchronous rotation (NSR), and physical libration by comparing how well each model reproduces observed cycloids. To do this, I have designed and implemented an automated parameter-searching algorithm that relies on a quantitative measure of fit quality to identify the best fits to observed cycloids. I apply statistical techniques to determine the tidal model best supported by the data and constrain the values of Europa's rotational parameters. Cycloids indicate a time-varying obliquity of about 1° and a physical libration in phase with the eccentricity libration, with amplitude >1°. To obtain good fits, cycloids must be translated in longitude, which implies non-synchronous rotation of the icy shell. However, stress from NSR is not well-supported, indicating that the rotation rate is slow enough that these stresses relax. I build upon the results of cycloid modeling in the second section by applying calculations of tidal stress that include obliquity to the formation of strike-slip faults. I predict the slip directions of faults with the standard formation model---tidal walking (Chapter 5)---and with a new mechanical model I have developed, called shell tectonics (Chapter 6). The shell tectonics model incorporates linear elasticity to determine slip and stress
Tectonic Plates of China

DTIC Science & Technology

1977-04-01

C. Sun and Ta-iang Teng Contractor: University of Southern California Principal Investigator: Professor Ta-liang Teng (213) 746-6124 Contract Number...83 i" I. INTRODUCTION Over the vast Chinese mainland, one of the most interesting and dynamic regions of the world, complex tectonics, coupled with...west Pacific and the Alpine- Himalaya tectonic belts, the multitude of Chinese tectonic com- plexities is evident from its enormous topographic relief
Recognizing human activities using appearance metric feature and kinematics feature

NASA Astrophysics Data System (ADS)

Qian, Huimin; Zhou, Jun; Lu, Xinbiao; Wu, Xinye

2017-05-01

The problem of automatically recognizing human activities from videos through the fusion of the two most important cues, appearance metric feature and kinematics feature, is considered. And a system of two-dimensional (2-D) Poisson equations is introduced to extract the more discriminative appearance metric feature. Specifically, the moving human blobs are first detected out from the video by background subtraction technique to form a binary image sequence, from which the appearance feature designated as the motion accumulation image and the kinematics feature termed as centroid instantaneous velocity are extracted. Second, 2-D discrete Poisson equations are employed to reinterpret the motion accumulation image to produce a more differentiated Poisson silhouette image, from which the appearance feature vector is created through the dimension reduction technique called bidirectional 2-D principal component analysis, considering the balance between classification accuracy and time consumption. Finally, a cascaded classifier based on the nearest neighbor classifier and two directed acyclic graph support vector machine classifiers, integrated with the fusion of the appearance feature vector and centroid instantaneous velocity vector, is applied to recognize the human activities. Experimental results on the open databases and a homemade one confirm the recognition performance of the proposed algorithm.
A new plate tectonic concept for the eastern-most Mediterranean

NASA Astrophysics Data System (ADS)

Huebscher, C.; McGrandle, A.; Scaife, G.; Spoors, R.; Stieglitz, T.

2012-04-01

Owing to the seismogenic faults bordering the Levant-Sinai realm and the discovery of giant gas reservoirs in the marine Levant Basin the scientific interest in this tectonically complex setting increased in recent years. Here we provide a new model for the Levant Basin architecture and adjacent plate boundaries emphasizing the importance of industrial seismic data for frontier research in earth science. PSDM seismics, residual gravity and depth to basement maps give a clear line of evidence that the Levant Basin, formerly considered as a single tectonic entity, is divided into two different domains. Highly stretched continental crust in the southern domain is separated from deeper and presumably Tethyan oceanic crust in the north. A transform continuing from southwest Cyprus to the Carmel Fault in northern Israel is considered as the boundary. If this interpretation holds, the Carmel-Cyprus Transform represents a yet unknown continent-ocean boundary in the eastern Mediterranean, thus adding new constrains for the Mediterranean plate tectonic puzzle. The Eratosthenes Seamount, considered as the spearhead of incipient continental collision in the eastern Mediterranean, is interpreted as a carbonate platform that developed above a volcanic basement. NW-SE trending strike-slip faults are abundant in the entire Levant region. Since this trend also shapes the topography of the Levant hinterland including Quaternary deposits their recent tectonic activity is quite likely. Thus, our study supports previous studies which attributed the evolution of submarine canyons and Holocene triggering of mass failures not only to salt tectonics or depositional processes, but also to active plate-tectonics.
Euro-African MAGSAT anomaly-tectonic observations

NASA Technical Reports Server (NTRS)

Hinze, W. J.; Olivier, R.; Vonfrese, R. R. B.

1985-01-01

Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.
Euro-african MAGSAT Anomaly-tectonic Observations

NASA Technical Reports Server (NTRS)

Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator); Olivier, R.

1984-01-01

Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.
Pore-pressure sensitivities to dynamic strains: observations in active tectonic regions

USGS Publications Warehouse

Barbour, Andrew J.

2015-01-01

Triggered seismicity arising from dynamic stresses is often explained by the Mohr-Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid-saturated rock. The seismic response of a fluid-rock system naturally depends on its hydro-mechanical properties, but accurately assessing how pore-fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore-pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 through 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling-response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends non-linearly on the inverse fault-perpendicular distance, with the response decreasing towards the fault; the SJB cluster is at the northern transition from creeping-to-locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength
Active tectonics at the Lower Yarmouk Gorge?

NASA Astrophysics Data System (ADS)

Inbar, Nimrod; Raggad, Marwan; Siebert, Christian; Möller, Peter; Rödiger, Tino; Rosenthal, Eliyaho; Guttman, Josseph; Magri, Fabien

2017-04-01

The Lower Yarmouk Gorge (LYG) extends on the eastern margin of the Jordan Rift Valley (JRV) adjacent to the Kinneret basin which makes part in the chain of pull-apart basins along the Dead Sea Transform (DST). The LYG is bounded to the south by the Ajloun Plateau (northern Jordan) and to the north by the Golan Heights (Israel). It acts as the outflow of the Yarmouk drainage basin into the Jordan River a few kilometers south of Lake Tiberias. Although topographically the Golan Heights and the Ajloun seem to be different provinces separated by the LYG, the northern Ajloun and southern Golan form the southern flank of a major synclinal structure. Morphologically, the LYG resembles the Sheikh-Ali strike-slip fault and other NE-SW striking faults related to the DST. However, the existence of faulting along that line is debatable. As the gorge serves also as state boundary, no seismic lines cross the LYG. Quaternary landslides, mostly on the southern flank of the LYG cover possible surface evidence of faulting although Quaternary basalts located at the gorge path may indicate possible vertical pathways. Moreover, hydrological studies (Siebert et al., 2014, Goretzki et al., 2016) show that permeability anisotropy along the LYG line allows heated groundwater to emerge along the gorge with temperatures rising up to 60°C. The presented study uses well data from northern Jordan and southern Golan Heights as well as seismic data from the southern Golan Heights to bridge over the information gap. Based on the available information we present our hypothesis on the geology of the LYG aiming to contribute to the discussion regarding active tectonics at the Lower Yarmouk Gorge. Our preliminary results show that a major fault along the gorge path is dubious however, perpendicular faulting is more likely to occur. We expect the results of current research to contribute to the understanding of the local complex geohydrological system. Furthermore, results are expected to deepen our
Photogeological analysis of Europan tectonic features

NASA Technical Reports Server (NTRS)

Tufts, B. R.

1993-01-01

Preliminary photogeological analyses of the Pelorus Linea and Sidon Flexus regions of Europa were conducted to explore the proposal by Schenk that lateral motion of crustal blocks has occurred in a 'rift zone' including possible strike-slip, tension fracturing, and geometric plate rotation about an Euler pole. These analyses revealed features interpreted as tensional structures and block rotation in a strike-slip regime consistent with the Schenk hypotheses and implied the presence of at least two stages of crustal deformation consistent with a chronology developed by Lucchitta. Confirmation of regional scale Euler pole rotation was ambiguous, however. Up to 80 kilometers of possible extension was identified in the rift zone; to accommodate this, 'cryosubduction' is speculatively proposed as a mechanism for recycling Europan 'ice lithosphere'. The cumulative width of wedge-shaped bands included in the rift zone was measured and plotted versus distance from the inferred rotation pole. Three sharp decreases in the total width were noted. These occur roughly where certain triple bands cross the rift zone suggesting that the bands are structural features that predate and influence the zone. While the curve hints at one or more sinusoidal relationships consistent with rotation geometry, given the low photographic resolution and the preliminary nature of this examination the question of whether the observations represent coherent regional rotation modified by crosscutting structures or instead imply independent local rotations separated by these structures is unanswered by this analysis.
Identifying tectonic parameters that affect tsunamigenesis

NASA Astrophysics Data System (ADS)

van Zelst, I.; Brizzi, S.; Heuret, A.; Funiciello, F.; van Dinther, Y.

2016-12-01

The role of tectonics in tsunami generation is at present poorly understood. However, the fact thatsome regions produce more tsunamis than others indicates that tectonics could influencetsunamigenesis. Here, we complement a global earthquake database that contains geometrical,mechanical, and seismicity parameters of subduction zones with tsunami data. We statisticallyanalyse the database to identify the tectonic parameters that affect tsunamigenesis. The Pearson'sproduct-moment correlation coefficients reveal high positive correlations of 0.65 between,amongst others, the maximum water height of tsunamis and the seismic coupling in a subductionzone. However, these correlations are mainly caused by outliers. The Spearman's rank correlationcoefficient results in statistically significant correlations of 0.60 between the number of tsunamisin a subduction zone and subduction velocity (positive correlation) and the sediment thickness atthe trench (negative correlation). Interestingly, there is a positive correlation between the latter andtsunami magnitude. These bivariate statistical methods are extended to a binary decision tree(BDT) and multivariate analysis. Using the BDT, the tectonic parameters that distinguish betweensubduction zones with tsunamigenic and non-tsunamigenic earthquakes are identified. To assessphysical causality of the tectonic parameters with regard to tsunamigenesis, we complement ouranalysis by a numerical study of the most promising parameters using a geodynamic seismic cyclemodel. We show that the inclusion of sediments on the subducting plate results in an increase insplay fault activity, which could lead to larger vertical seafloor displacements due to their steeperdips and hence a larger tsunamigenic potential. We also show that the splay fault is the preferredrupture path for a strongly velocity strengthening friction regime in the shallow part of thesubduction zone, which again increases the tsunamigenic potential.

Tectonic history of the Syria Planum province of Mars

USGS Publications Warehouse

Tanaka, K.L.; Davis, P.A.

1988-01-01

We attribute most of the development of extensive fractures in the Tharsis region to discrete tectonic provinces within the region, rather than to Tharsis as a single entity. One of these provinces is in Syria Planum. Faults and collapse structures in the Syria Planum tectonic province on Mars are grouped into 13 sets based on relative age, areal distribution, and morphology. According to superposition and fault crosscutting relations and crater counts we designate six distinct episodes of tectonic activity. Photoclinometric topographic profiles across 132 grabens and fault scarps show that Syria Planum grabens have widths (average of 2.5 km, and most range from 1 to 6 km) similar to lunar grabens, but the Martian grabens have slightly higher side walls (average abour 132 m) and gentler wall slopes (average of 9?? and range of 2??-25??) than lunar grabens (93 m high and 18?? slopes). Estimates of the amount of extension for individual grabens range from 20 to 350 m; most estimates of the thickness of the faulted layer range from 0.5 to 4.5 km (average is 1.5 km). This thickness range corresponds closely to the 0.8- to 3.6-km range in depth for pits, troughs, and canyons in Noctis Labyrinthus and along the walls of Valles Marineris. We propose that the predominant 1- to 1.5-km values obtained for both the thickness of the faulted layer and the depths of the pits, troughs, and theater heads of the canyons reflect the initial depth to the water table in this region, as governed by the depth to the base of ground ice. Maximum depths for these features may indicate lowered groundwater table depths and the base of ejecta material. -from Authors
Easy handling of tectonic data: the programs TectonicVB for Mac and TectonicsFP for Windows™

NASA Astrophysics Data System (ADS)

Ortner, Hugo; Reiter, Franz; Acs, Peter

2002-12-01

TectonicVB for Macintosh and TectonicsFP for Windows TM operating systems are two menu-driven computer programs which allow the shared use of data on these environments. The programs can produce stereographic plots of orientation data (great circles, poles, lineations). Frequently used statistical procedures like calculation of eigenvalues and eigenvectors, calculation of mean vector with concentration parameters and confidence cone can be easily performed. Fault data can be plotted in stereographic projection (Angelier and Hoeppener plots). Sorting of datasets into homogeneous subsets and rotation of tectonic data can be performed in interactive two-diagram windows. The paleostress tensor can be calculated from fault data sets using graphical (calculation of kinematic axes and right dihedra method) or mathematical methods (direct inversion or numerical dynamical analysis). The calculations can be checked in dimensionless Mohr diagrams and fluctuation histograms.
Tectonic tests of proposed polar wander paths for Mars and the moon

NASA Technical Reports Server (NTRS)

Grimm, R. E.; Solomon, S. C.

1986-01-01

A comparison of the lithospheric stress field predicted for rapid global reorientations against observed tectonic features is used to test the polar wander paths proposed for Mars by Schultz and Lutz-Garihan (1981). A calculation of the reorientation stresses leads to the suggestion that the formation of normal faults or graben in broad regions around the former rotation poles should be the minimum tectonic signature of a reorientation that generates lithospheric stresses in excess of the extensional strength of near-surface material. It is concluded that polar wander of the magnitude and timing envisioned by Schultz and Lutz-Garihan did not occur.
A mechanism for tectonic deformation on Venus

NASA Technical Reports Server (NTRS)

Phillips, Roger J.

1986-01-01

In the absence of identifiable physiographic features directly associated with plate tectonics, alternate mechanisms are sought for the intense tectonic deformation observed in radar images of Venus. One possible mechanism is direct coupling into an elastic lithosphere of the stresses associated with convective flow in the interior. Spectral Green's function solutions have been obtained for stresses in an elastic lithosphere overlying a Newtonian interior with an exponential depth dependence of viscosity, and a specified surface-density distribution driving the flow. At long wavelengths and for a rigid elastic/fluid boundary condition, horizontal normal stresses in the elastic lid are controlled by the vertical shear stress gradient and are directly proportional to the depth of the density disturbance in the underlying fluid. The depth and strength of density anomalies in the Venusian interior inferred by analyses of long wavelength gravity data suggest that stresses in excess of 100 MPa would be generated in a 10 km thick elastic lid unless a low viscosity channel occurring beneath the lid or a positive viscosity gradient uncouples the flow stresses. The great apparent depth of compensation of topographic features argues against this, however, thus supporting the importance of the coupling mechanism. If there is no elastic lid, stresses will also be very high near the surface, providing also that the viscosity gradient is negative.
Geodetic component of the monitoring of tectonic and hydrogeological activities in Kopacki Rit Nature Park

NASA Astrophysics Data System (ADS)

Dapo, Almin; Pribicevic, Bosko

2013-04-01

Based on the European and global experience, the amplitude change in the structural arrangement caused by recent tectonic movements, can be most accurately determined by repeated precise GPS measurements on specially stabilized geodetic and geodynamic points. Because of these reasons, the GPS method to determine the movements on specially stabilized points in the Nature park Kopacki rit is also applied in this project. Kopacki rit Nature Park is the biggest preserved natural flooded area on the Danube. It is spread over 23 000 hectares between the rivers Danube and Drava and is one of the biggest fluvial wetland valleys in Europe. In 1993 it was listed as one of internationally valuable wetlands according to the Ramsar Convention. By now in Kopacki rit there have been sights of about 295 bird species, more than 400 species of invertebrates and 44 types of fish. Many of them are globally endangered species like, white tailed eagle, black stork and prairie hawk. It's not rare to come across some deer herds, wild boars or others. Today's geological and geomorphological relations in the Nature park Kopacki rit are largely the result of climate, sedimentary, tectonic and anthropogenic activity in the last 10,000 years. Unfortunately the phenomenon of the Kopacki rit Nature park is in danger to be over in the near future due to those and of course man made activities on the Danube river. It is trough scientific investigations of tectonic and hydrogeological activities that scientist from University of Zagreb are trying to contribute to wider knowledge and possible solutions to this problem. In the year 2009 the first GPS campaign was conducted, and the first set of coordinates of stabilized points was determined which can be considered zero-series measurements. In 2010 a second GPS campaign was conducted and the first set of movements on the Geodynamic Network of Kopacki Rit Nature Park was determined. Processing GPS measurements from 2009 and 2010 was carried out in a
GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany)

PubMed Central

Berberich, Gabriele; Schreiber, Ulrich

2013-01-01

Simple Summary In a 1.140 km² study area of the volcanic West Eifel, approx. 3,000 Red Wood Ant (RWA; Formica rufa-group) mounds had been identified and correlated with tectonically active gas-permeable faults, mostly strike-slip faults. Linear alignment of RWA mounds and soil gas anomalies distinctly indicate the course of these faults, while clusters of mounds indicate crosscut zones of fault systems, which can be correlated with voids caused by crustal block rotation. This demonstrates that RWA are bioindicators for identifying active fault systems and useful where information on the active regime is incomplete or the resolution by technical means is insufficient. Abstract In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO2, Helium, Radon and H2S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H2S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel
Computer-based self-organized tectonic zoning: a tentative pattern recognition for Iran

NASA Astrophysics Data System (ADS)

Zamani, Ahmad; Hashemi, Naser

2004-08-01

Conventional methods of tectonic zoning are frequently characterized by two deficiencies. The first one is the large uncertainty involved in tectonic zoning based on non-quantitative and subjective analysis. Failure to interpret accurately a large amount of data "by eye" is the second. In order to alleviate each of these deficiencies, the multivariate statistical method of cluster analysis has been utilized to seek and separate zones with similar tectonic pattern and construct automated self-organized multivariate tectonic zoning maps. This analytical method of tectonic regionalization is particularly useful for showing trends in tectonic evolution of a region that could not be discovered by any other means. To illustrate, this method has been applied for producing a general-purpose numerical tectonic zoning map of Iran. While there are some similarities between the self-organized multivariate numerical maps and the conventional maps, the cluster solution maps reveal some remarkable features that cannot be observed on the current tectonic maps. The following specific examples need to be noted: (1) The much disputed extent and rigidity of the Lut Rigid Block, described as the microplate of east Iran, is clearly revealed on the self-organized numerical maps. (2) The cluster solution maps reveal a striking similarity between this microplate and the northern Central Iran—including the Great Kavir region. (3) Contrary to the conventional map, the cluster solution maps make a clear distinction between the East Iranian Ranges and the Makran Mountains. (4) Moreover, an interesting similarity between the Azarbaijan region in the northwest and the Makran Mountains in the southeast and between the Kopet Dagh Ranges in the northeast and the Zagros Folded Belt in the southwest of Iran are revealed in the clustering process. This new approach to tectonic zoning is a starting point and is expected to be improved and refined by collection of new data. The method is also a useful
Tectonic Divisions Based on Gravity Data and Earthquake Distribution Characteristics in the North South Seismic Belt, China

NASA Astrophysics Data System (ADS)

Tian, T.; Zhang, J.; Jiang, W.

2017-12-01

The North South Seismic Belt is located in the middle of China, and this seismic belt can be divided into 12 tectonic zones, including the South West Yunnan (I), the Sichuan Yunnan (II), the Qiang Tang (III), the Bayan Har (IV), the East Kunlun Qaidam (V), the Qi Lian Mountain (VI), the Tarim(VII), the East Alashan (VIII), the East Sichuan (IX), the Ordos(X), the Middle Yangtze River (XI) and the Edge of Qinghai Tibet Block (XII) zone. Based on the Bouguer Gravity data calculated from the EGM2008 model, the Euler deconvolution was used to obtain the edge of tectonic zone to amend the traditional tectonic divisions. In every tectonic zone and the whole research area, the logarithm of the total energy of seismic was calculated. The Time Series Analysis (TSA) for all tectonic zones and the whole area were progressed in R, and 12 equal divisions were made (A1-3, B1-3, C1-3, D1-3) by latitude and longitude as a control group. A simple linear trend fitting of time was used, and the QQ figure was used to show the residual distribution features. Among the zones according to Gravity anomalies, I, II and XII show similar statistical characteristic, with no earthquake free year (on which year there was no earthquake in the zone), and it shows that the more seismic activity area is more similar in statistical characteristic as the large area, no matter how large the zone is or how many earthquakes are in the zone. Zone IV, V, IX, III, VII and VIII show one or several seismic free year during 1970s (IV, V and IX) and 1980s (III, VII and VIII), which may implicate the earthquake activity were low decades ago or the earthquake catalogue were not complete in these zones, or both. Zone VI, X and XI show many earthquake free years even in this decade, which means in these zones the earthquake activity were very low even if the catalogue were not complete. In the control group, the earthquake free year zone appeared random and independent of the seismic density, and in all equal
Global Patterns of Tectonism on Titan from Mountain Chains and Virgae

NASA Technical Reports Server (NTRS)

Cook, C.; Barnes, J. W.; Radebaugh, J.; Hurford, T.; Ktatenhorn, S. A.

2012-01-01

This research is based on the exploration of tectonic patterns on Titan from a global perspective. Several moons in the outer solar system display patterns of surface tectonic features that imply global stress fields driven or modified by global forces. Patterns such as these are seen in Europa's tidally induced fracture patterns, Enceladus's tiger stripes, and Ganymede's global expansion induced normal fault bands. Given its proximity to Saturn, as well as its eccentric orbit, tectonic features and global stresses may be present on Titan as well. Titan displays possible tectonic structures, such as mountain chains along its equator (Radebaugh et al. 2007), as well as the unexplored dark linear streaks termed virgae by the IAU. Imaged by Cassini with the RADAR instrument, mountain chains near the equator are observed with a predominante east-west orientation (Liu et al. 2012, Mitri et al. 2010). Orientations such as these can be explained by modifications in the global tidal stress field induced by global contraction followed by rotational spin-up. Also, due to Titan's eccentric orbit, its current rotation rate may be in an equilibrium between tidal spin-up near periapsis and spin-down near apoapsis (Barnes and Fortney 2003). Additional stress from rotational spin-up provides an asymmetry to the stress field. This, combined with an isotropic stress from radial contraction, favors the formation of equatorial mountain chains in an east-west direction. The virgae, which have been imaged by Cassini with both the Visual and Infrared Mapping Spectrometer (VIMS) and Imaging Science Subsystem (ISS) instruments, are located predominately near 30 degrees latitude in either hemisphere. Oriented with a pronounced elongation in the east-west direction, all observed virgae display similar characteristics: similar relative albedos as the surrounding terrain however darkened with an apparent neutral absorber, broken-linear or rounded sharp edges, and connected, angular elements
Venus tectonics - Initial analysis from Magellan

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Head, James W.; Kaula, William M.; Schubert, Gerald; Mckenzie, Dan

1991-01-01

The styles of lithospheric deformation, the inferred mechanical properties of the lithosphere, and their implications for the tectonic history of Venus are discussed on the basis of radar imaging and altimetry data from Magellan. Observations of the planet plains reveal a superposition of different episodes of deformation and volcanism, strain both distributed and concentrated into zones of extension and shortening, and features reflecting a crustal response to mantle dynamic processes. Lithospheric shortening and crustal thickening are represented by ridge belts and mountain belts. The latter show the evidence for extension and collapse both during and following crustal compression. Venus displays quasi-circular coronae and broad rises with linear rift zones, associated with significant volcanism. Large-offset strike-slip faults have not been observed, although horizontal shear is accommodated across broad zones of crustal shortening. On Venus strain is distributed across zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on earth.
The Black Mountain tectonic zone--a reactivated northeast-trending crustal shear zone in the Yukon-Tanana Upland of east-central Alaska: Chapter D in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

USGS Publications Warehouse

O'Neill, J. Michael; Day, Warren C.; Alienikoff, John N.; Saltus, Richard W.; Gough, Larry P.; Day, Warren C.

2007-01-01

The Black Mountain tectonic zone in the YukonTanana terrane of east-central Alaska is a belt of diverse northeast-trending geologic features that can been traced across Black Mountain in the southeast corner of the Big Delta 1°×3° degree quadrangle. Geologic mapping in the larger scale B1 quadrangle of the Big Delta quadrangle, in which Black Mountain is the principal physiographic feature, has revealed a continuous zone of normal and left-lateral strikeslip high-angle faults and shear zones, some of which have late Tertiary to Quaternary displacement histories. The tectonic zone includes complexly intruded wall rocks and intermingled apophyses of the contiguous mid-Cretaceous Goodpaster and Mount Harper granodioritic plutons, mafic to intermediate composite dike swarms, precious metal mineralization, early Tertiary volcanic activity and Quaternary fault scarps. These structures define a zone as much as 6 to 13 kilometers (km) wide and more than 40 km long that can be traced diagonally across the B1 quadrangle into the adjacent Eagle 1°×3° quadrangle to the east. Recurrent activity along the tectonic zone, from at least mid-Cretaceous to Quaternary, suggests the presence of a buried, fundamental tectonic feature beneath the zone that has influenced the tectonic development of this part of the Yukon-Tanana terrane. The tectonic zone, centered on Black Mountain, lies directly above a profound northeast-trending aeromagnetic anomaly between the Denali and Tintina fault systems. The anomaly separates moderate to strongly magnetic terrane on the northwest from a huge, weakly magnetic terrane on the southeast. The tectonic zone is parallel to the similarly oriented left-lateral, strike-slip Shaw Creek fault zone 85 km to the west.
Tectonic significance of Kibaran structures in Central and Eastern Africa

NASA Astrophysics Data System (ADS)

Rumvegeri, B. T.

Tectonical movements of the Kibaran belt (1400-950 Ma) can be subdivided into two major deformation events, corresponding to tight, upright or recumbent folds, thrust faults, nappes and stretching lineation with a general plunging southwards. At the regional scale, the stretching lineation, associated with thrust faults and nappes is interpreted as an indication of a northwards moving direction. The shear zone with mafic-ultramafic rocks across Burundi, MW-Tanzania, SW-Uganda and NE-Zaïre is the suture zone of the Kibaran belt. Kibaran metamorphism is plurifacial and has four epizodes. The second, syn-D2, is the most important and constitutes the climax; it reached the granulite facies. The succession of tectonic, metamorphic and magmatic features suggests geotectonic evolution by subduction-collision.
Present tectonics of the southeast of Russia as seen from GPS observations

NASA Astrophysics Data System (ADS)

Shestakov, N. V.; Gerasimenko, M. D.; Takahashi, H.; Kasahara, M.; Bormotov, V. A.; Bykov, V. G.; Kolomiets, A. G.; Gerasimov, G. N.; Vasilenko, N. F.; Prytkov, A. S.; Timofeev, V. Yu.; Ardyukov, D. G.; Kato, T.

2011-02-01

The present tectonics of Northeast Asia has been extensively investigated during the last 12 yr by using GPS techniques. Nevertheless, crustal velocity field of the southeast of Russia near the northeastern boundaries of the hypothesized Amurian microplate has not been defined yet. The GPS data collected between 1997 February and 2009 April at sites of the regional geodynamic network were used to estimate the recent geodynamic activity of this area. The calculated GPS velocities indicate almost internal (between network sites) and external (with respect to the Eurasian tectonic plate) stability of the investigated region. We have not found clear evidences of any notable present-day tectonic activity of the Central Sikhote-Alin Fault as a whole. This fault is the main tectonic unit that determines the geological structure of the investigated region. The obtained results speak in favour of the existence of a few separate blocks and a more sophisticated structure of the proposed Amurian microplate in comparison with an indivisible plate approach.
Identification and interpretation of tectonic features from ERTS-1 imagery: Southwestern North America and the Red Sea area

NASA Technical Reports Server (NTRS)

Abdel-Gawad, M. (Principal Investigator); Tubbesing, L.

1975-01-01

The author has identified the following significant results. The ERTS-1 imagery was utilized to study major fault and tectonic lines and their intersections in southwestern North America. A system of transverse shear faults was recognized in the California Coast Ranges, the Sierra Nevada, the Great Basin, and Mexico. They are interpreted as expressions of a major left-lateral shear which predated the San Andreas system, the opening of the Gulf of California and Basin and Range rift development. Tectonic models for Basin and Range, Coast Ranges, and Texas-Parras shears were developed. Geological structures and Precambrian metamorphic trend lines of schistosity were studied across the Red Sea rift.
Transverse tectonic structural elements across Himalayan mountain front, eastern Arunachal Himalaya, India: Implication of superposed landform development on analysis of neotectonics

NASA Astrophysics Data System (ADS)

Bhakuni, S. S.; Luirei, Khayingshing; Kothyari, Girish Ch.; Imsong, Watinaro

2017-04-01

Structural and morphotectonic signatures in conjunction with the geomorphic indices are synthesised to trace the role of transverse tectonic features in shaping the landforms developed along the frontal part of the eastern Arunachal sub-Himalaya. Mountain front sinuosity (Smf) index values close to one are indicative of the active nature of the mountain front all along the eastern Arunachal Himalaya, which can be directly attributed to the regional uplift along the Himalayan Frontal Thrust (HFT). However, the mountain front is significantly sinusoidal around junctions between HFT/MBT (Main Boundary Thrust) and active transverse faults. The high values of stream length gradient (SL) and stream steepness (Ks) indices together with field evidence of fault scarps, offset of terraces, and deflection of streams are markers of neotectonic uplift along the thrusts and transverse faults. This reactivation of transverse faults has given rise to extensional basins leading to widening of the river courses, providing favourable sites for deposition of recent sediments. Tectonic interactions of these transverse faults with the Himalayan longitudinal thrusts (MBT/HFT) have segmented the mountain front marked with varying sinuosity. The net result is that a variety of tectonic landforms recognized along the mountain front can be tracked to the complex interactions among the transverse and longitudinal tectonic elements. Some distinctive examples are: in the eastern extremity of NE Himalaya across the Dibang River valley, the NW-SE trending mountain front is attenuated by the active Mishmi Thrust that has thrust the Mishmi crystalline complex directly over the alluvium of the Brahmaputra plains. The junction of the folded HFT and Mishmi Thrust shows a zone of brecciated and pulverized rocks along which transverse axial planar fracture cleavages exhibit neotectonic activities in a transverse fault zone coinciding with the Dibang River course. Similarly, the transverse faults cut the
Active tectonics and drainage evolution in the Tunisian Atlas driven by interaction between crustal shortening and slab pull

NASA Astrophysics Data System (ADS)

Camafort, Miquel; Booth-Rea, Guillermo; Pérez-Peña, Jose Vicente; Melki, Fetheddine; Gracia, Eulalia; Azañón, Jose Miguel; Ranero, César R.

2017-04-01

Active tectonics in North Africa is fundamentally driven by NW-SE directed slow convergence between the Nubia and Eurasia plates, leading to a region of thrust and strike-slip faulting. In this paper we analyze the morphometric characteristics of the little-studied northern Tunisia sector. The study aimed at identifying previously unknown active tectonic structures, and to further understand the mechanisms that drive the drainage evolution in this region of slow convergence. The interpretation of morphometric data was supported with a field campaign of a selection of structures. The analysis indicates that recent fluvial captures have been the main factor rejuvenating drainage catchments. The Medjerda River, which is the main catchment in northern Tunisia, has increased its drainage area during the Quaternary by capturing adjacent axial valleys to the north and south of its drainage divide. These captures are probably driven by gradual uplift of adjacent axial valleys by reverse/oblique faults or associated folds like El Alia-Teboursouk and Dkhila faults. Our fieldwork found that these faults cut Holocene colluvial fans containing seismites like clastic dikes and sand volcanoes, indicating recent seismogenic faulting. The growth and stabilization of the axial Medjerda River against the natural tendency of transverse drainages might be caused by a combination of dynamic topography and transpressive tectonics. The orientation of the large axial Medjerda drainage that runs from eastern Algeria towards northeastern Tunisia into the Gulf of Tunis, might be the associated to negative buoyancy caused by the underlying Nubia slab at its mouth, together with uplift of the Medjerda headwaters along the South Atlassic dextral transfer zone.
A test of the hypothesis that impact-induced fractures are preferred sites for later tectonic activity

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Duxbury, Elizabeth D.

1987-01-01

Impact cratering has been an important process in the solar system. The cratering event is generally accompanied by faulting in adjacent terrain. Impact-induced faults are nearly ubiquitous over large areas on the terrestrial planets. The suggestion is made that these fault systems, particularly those associated with the largest impact features are preferred sites for later deformation in response to lithospheric stresses generated by other processes. The evidence is a perceived clustering of orientations of tectonic features either radial or concentric to the crater or basin in question. An opportunity exists to test this suggestion more directly on Earth. The terrestrial continents contain more than 100 known or probable impact craters, with associated geological structures mapped to varying levels of detail. Prime facie evidence for reactivation of crater-induced faults would be the occurrence of earthquakes on these faults in response to the intraplate stress field. Either an alignment of epicenters with mapped fault traces or fault plane solutions indicating slip on a plane approximately coincident with that inferred for a crater-induced fault would be sufficient to demonstrate such an association.
Differential preservation in the geologic record of intraoceanic arc sedimentary and tectonic processes

USGS Publications Warehouse

Draut, Amy; Clift, Peter D.

2013-01-01

Records of ancient intraoceanic arc activity, now preserved in continental suture zones, are commonly used to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc–continent collision is complicated by preferential preservation of evidence for some arc processes and loss of evidence for others. In this synthesis we examine what is lost, and what is preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc–continent collision geometry. ‘Forward-facing’ collision can accrete an oceanic arc on to either a passive or an active continental margin, with the arc facing the continent and colliding trench- and forearc-side first. In a ‘backward-facing’ collision, involving two subduction zones with similar polarity, the arc collides backarc-first with an active continental margin. The preservation of evidence for contemporary sedimentary and tectonic arc processes in the geologic record depends greatly on how well the various parts of the arc survive collision and orogeny in each case. Preservation of arc terranes likely is biased towards those that were in a state of tectonic accretion for tens of millions of years before collision, rather than tectonic erosion. The prevalence of tectonic erosion in modern intraoceanic arcs implies that valuable records of arc processes are commonly destroyed even before the arc collides with a continent. Arc systems are most likely to undergo tectonic accretion shortly before forward-facing collision with a continent, and thus most forearc and accretionary-prism material in ancient arc terranes likely is temporally biased toward the final stages of arc activity, when sediment flux to the trench was greatest and tectonic accretion prevailed. Collision geometry
Studies of oceanic tectonics based on GEOS-3 satellite altimetry

NASA Technical Reports Server (NTRS)

Poehls, K. A.; Kaula, W. M.; Schubert, G.; Sandwell, D.

1979-01-01

Using statistical analysis, geoidal admittance (the relationship between the ocean geoid and seafloor topography) obtained from GEOS-3 altimetry was compared to various model admittances. Analysis of several altimetry tracks in the Pacific Ocean demonstrated a low coherence between altimetry and seafloor topography except where the track crosses active or recent tectonic features. However, global statistical studies using the much larger data base of all available gravimetry showed a positive correlation of oceanic gravity with topography. The oceanic lithosphere was modeled by simultaneously inverting surface wave dispersion, topography, and gravity data. Efforts to incorporate geoid data into the inversion showed that the base of the subchannel can be better resolved with geoid rather than gravity data. Thermomechanical models of seafloor spreading taking into account differing plate velocities, heat source distributions, and rock rheologies were discussed.
Using Grand Challenges For Innovative Teaching in Structural Geology, Geophysics, and Tectonics

NASA Astrophysics Data System (ADS)

McDaris, J. R.; Tewksbury, B. J.; Wysession, M. E.

2012-12-01

An innovative approach to teaching involves using the "Big Ideas" or "Grand Challenges" of a field, as determined by the research community in that area, as the basis for classroom activities. There have been several recent efforts in the areas of structural geology, tectonics, and geophysics to determine these Grand Challenges, including the areas of seismology ("Seismological Grand Challenges in Understanding Earth's Dynamic Systems"), mineral physics ("Unlocking the Building Blocks of the Planet"), EarthScope-related science ("Unlocking the Secrets of the North American Continent: An EarthScope Science Plan for 2010-2020"), and structural geology and tectonics (at the Structural Geology and Tectonics Forum held at Williams College in June, 2012). These research community efforts produced frameworks of the essential information for their fields with the aim of guiding future research. An integral part of this, however, is training the next generation of scientists, and using these Big Ideas as the basis for course structures and activities is a powerful way to make this happen. When activities, labs, and homeworks are drawn from relevant and cutting-edge research topics, students can find the material more fascinating and engaging, and can develop a better sense of the dynamic process of scientific discovery. Many creative ideas for incorporating the Grand Challenges of structural geology, tectonics, and geophysics in the classroom were developed at a Cutting Edge workshop on "Teaching Structural Geology, Geophysics, and Tectonics in the 21st Century" held at the University of Tennessee in July, 2012.

Crustal Magnetic Field Anomalies and Global Tectonics

NASA Astrophysics Data System (ADS)

Storetvedt, Karsten

2014-05-01

A wide variety of evidence suggests that the ruling isochron (geomagnetic polarity versus age) hypothesis of marine magnetic lineations has no merit - undermining therefore one of the central tenets of plate tectonics. Instead, variable induction by the ambient geomagnetic field is likely to be the principal agent for mega-scale crustal magnetic features - in both oceanic and continental settings. This revitalizes the fault-controlled susceptibility-contrast model of marine magnetic lineations, originally proposed in the late 1960s. Thus, the marine magnetic 'striping' may be ascribed to tectonic shearing and related, but variable, disintegration of the original iron-oxide mineralogy, having developed primarily along one of the two pan-global sets of orthogonal fractures and faults. In this way, fault zones (having the more advanced mineral alteration) would be characterized by relatively low susceptibility, while more moderately affected crustal sections (located between principal fault zones) would be likely to have less altered oxide mineralogy and therefore higher magnetic susceptibility. On this basis, induction by the present geomagnetic field is likely to produce oscillating magnetic field anomalies with axis along the principal shear grain. The modus operandi of the alternative magneto-tectonic interpretation is inertia-driven wrenching of the global Alpine age palaeo-lithosphere - triggered by changes in Earth's rotation. Increasing sub-crustal loss to the upper mantle during the Upper Mesozoic had left the ensuing Alpine Earth in a tectonically unstable state. Thus, sub-crustal eclogitization and associated gravity-driven delamination to the upper mantle led to a certain degree of planetary acceleration which in turn gave rise to latitude-dependent, westward inertial wrenching of the global palaeo-lithosphere. During this process, 1) the thin and mechanically fragile oceanic crust were deformed into a new type of broad fold belts, and 2) the continents
Scaling and spatial complementarity of tectonic earthquake swarms

NASA Astrophysics Data System (ADS)

Passarelli, Luigi; Rivalta, Eleonora; Jónsson, Sigurjón; Hensch, Martin; Metzger, Sabrina; Jakobsdóttir, Steinunn S.; Maccaferri, Francesco; Corbi, Fabio; Dahm, Torsten

2018-01-01

Tectonic earthquake swarms (TES) often coincide with aseismic slip and sometimes precede damaging earthquakes. In spite of recent progress in understanding the significance and properties of TES at plate boundaries, their mechanics and scaling are still largely uncertain. Here we evaluate several TES that occurred during the past 20 years on a transform plate boundary in North Iceland. We show that the swarms complement each other spatially with later swarms discouraged from fault segments activated by earlier swarms, which suggests efficient strain release and aseismic slip. The fault area illuminated by earthquakes during swarms may be more representative of the total moment release than the cumulative moment of the swarm earthquakes. We use these findings and other published results from a variety of tectonic settings to discuss general scaling properties for TES. The results indicate that the importance of TES in releasing tectonic strain at plate boundaries may have been underestimated.
From Plate Tectonic to Continental Dynamics

NASA Astrophysics Data System (ADS)

Molnar, P. H.

2017-12-01

By the early 1970s, the basics of plate tectonics were known. Although much understanding remained to be gained, as a topic of research, plate tectonics no longer defined the forefront of earth science. Not only had it become a foundation on which to build, but also the methods used to reveal it became tools to take in new directions. For me as a seismologist studying earthquakes and active processes, the deformation of continents offered an obvious topic to pursue. Obviously examining the deformation of continents and ignoring the widespread geologic evidence of both ongoing and finite deformation of crust would be stupid. I was blessed with the opportunity to learn from and collaborate with two of the best, Paul Tapponnier and Clark Burchfiel. Continental deformation differed from plate tectonics both because deformation was widespread but more importantly because crust shortens (extends) horizontally and thickens (thins), processes that can be ignored where plate tectonics - the relative motion of rigid plates - occurs. Where a plate boundary passes into a continent, not only must the forces that move plates do work against friction or other dissipative processes, but where high terrain is created, they must also do work against gravity, to create gravitational potential energy in high terrain. Peter Bird and Kenneth Piper and Philip England and Dan McKenzie showed that a two-dimensional thin viscous sheet with vertically averaged properties enabled both sources of resistance to be included without introducing excessive complexity and to be scaled by one dimensionless number, what the latter pair called the Argand number. Increasingly over the past thirty years, emphasis has shifted toward the role played by the mantle lithosphere, because of both its likely strength and its negative buoyancy, which makes it gravitationally unstable. Despite progress since realizing that rigid plates (the essence of plate tectonics) provides a poor description of continental
Venus - Volcanic features in Atla Region

NASA Technical Reports Server (NTRS)

1991-01-01

This Magellan image from the Atla region of Venus shows several types of volcanic features and superimposed surface fractures. The area in the image is approximately 350 kilometers (217 miles) across, centered at 9 degrees south latitude, 199 degrees east longitude. Lava flows emanating from circular pits or linear fissures form flower-shaped patterns in several areas. A collapse depression approximately 20 kilometers by 10 kilometers (12 by 6 miles) near the center of the image is drained by a lava channel approximately 40 kilometers (25 miles) long. Numerous surface fractures and graben (linear valleys) criss-cross the volcanic deposits in north to northeast trends. The fractures are not buried by the lavas, indicating that the tectonic activity post-dates most of the volcanic activity.
Volcano-Tectonic Activity at Deception Island Volcano Following a Seismic Swarm in the Bransfield Rift (2014-2015)

NASA Astrophysics Data System (ADS)

Almendros, J.; Carmona, E.; Jiménez, V.; Díaz-Moreno, A.; Lorenzo, F.

2018-05-01

In September 2014 there was a sharp increase in the seismic activity of the Bransfield Strait, Antarctica. More than 9,000 earthquakes with magnitudes up to 4.6 located SE of Livingston Island were detected over a period of 8 months. A few months after the series onset, local seismicity at the nearby (˜35 km) Deception Island volcano increased, displaying enhanced long-period seismicity and several outbursts of volcano-tectonic (VT) earthquakes. Before February 2015, VT earthquakes occurred mainly at 5-20 km SW of Deception Island. In mid-February the numbers and sizes of VT earthquakes escalated, and their locations encompassed the whole volcanic edifice, suggesting a situation of generalized unrest. The activity continued in anomalously high levels at least until May 2015. Given the spatial and temporal coincidence, it is unlikely that the Livingston series and the Deception VT swarm were unrelated. We propose that the Livingston series may have produced a triggering effect on Deception Island volcano. Dynamic stresses associated to the seismic swarm may have induced overpressure in the unstable volcanic system, leading to a magmatic intrusion that may in turn have triggered the VT swarm. Alternatively, both the Livingston earthquakes and the VT swarm could be consequences of a magmatic intrusion at Deception Island. The Livingston series would be an example of precursory distal VT swarm, which seems to be a common feature preceding volcanic eruptions and magma intrusions in long-dormant volcanoes.
Tectonic control of complex slope failures in the Ameka River Valley (Lower Gibe Area, central Ethiopia): Implications for landslide formation

NASA Astrophysics Data System (ADS)

Kycl, Petr; Rapprich, Vladislav; Verner, Kryštof; Novotný, Jan; Hroch, Tomáš; Mišurec, Jan; Eshetu, Habtamu; Tadesse Haile, Ezra; Alemayehu, Leta; Goslar, Tomasz

2017-07-01

Even though major faults represent important landslide controlling factors, the role the tectonic setting in actively spreading rifts plays in the development of large complex landslides is seldom discussed. The Ameka complex landslide area is located on the eastern scarp of the Gibe Gorge, approximately 45 km to the west of the Main Ethiopian Rift and 175 km to the southwest of Addis Ababa. Investigation of the complex landslide failures required a combination of satellite and airborne data-based geomorphology, geological field survey complemented with structural analysis, radiocarbon geochronology and vertical electric sounding. The obtained observations confirmed the multiphase evolution of the landslide area. We have documented that, apart from climatic and lithological conditions, the main triggering factor of the Ameka complex landslide is the tectonic development of this area. The E-W extension along the NNE-SSW trending Main Ethiopian Rift is associated with the formation of numerous parallel normal faults, such as the Gibe Gorge fault and the almost perpendicular scissor faults. The geometry of the slid blocks of coherent lithology have inherited the original tectonic framework, which suggests the crucial role tectonics play in the fragmentation of the compact rock-masses, and the origin and development of the Ameka complex landslide area. Similarly, the main scarps were also parallel to the principal tectonic features. The local tectonic framework is dominated by faults of the same orientation as the regional structures of the Main Ethiopian Rift. Such parallel tectonic frameworks display clear links between the extension of the Main Ethiopian Rift and the tectonic development of the landslide area. The Ameka complex landslide developed in several episodes over thousands of years. According to the radiocarbon data, the last of the larger displaced blocks (representing only 2% of the total area) most likely slid down in the seventh century AD. The main
Quaternary Tectonic Tilting Governed by Rupture Segments Controls Surface Morphology and Drainage Evolution along the South-Central Coast of Chile

NASA Astrophysics Data System (ADS)

Echtler, H. P.; Bookhagen, B.; Melnick, D.; Strecker, M.

2004-12-01

The Chilean coast represents one of the most active convergent margins in the Pacific rim, where major earthquakes (M>8) have repeatedly ruptured the surface, involving vertical offsets of several meters. Deformation along this coast takes place in large-scale, semi-independent seismotectonic segments with partially overlapping transient boundaries. They are possibly related to reactivated inherited crustal anisotropies; internal seismogenic deformation may be accommodated by structures that have developed during accretionary wedge evolution. Seismotectonic segmentation and the identification of large-scale rupture zones, however, are based on limited seismologic und geodetic observations over short timespans. In order to better define the long-term behavior and deformation rates of these segments and to survey the tectonic impact on the landscape on various temporal and spatial scales, we investigated the south-central coast of Chile (37-38S). There, two highly active, competing seismotectonic compartments influence the coastal and fluvial morphology. A rigorous analysis of the geomorphic features is a key for an assessment of the tectonic evolution during the Quaternary and beyond. We studied the N-S oriented Santa María Island (SMI), 20 km off the coast and only ~70km off the trench, in the transition between the two major Valdivia (46-37S) and Concepción (38-35S) rupture segments. The SMI has been tectonically deformed throughout the Quaternary and comprises two tilt domains with two topographic highs in the north and south that are being tilted eastward. The low-lying and flat eastern part of the island is characterized by a set of emergent Holocene strandlines related to coseismic uplift. We measured detailed surface morphology of these strandlines and E-W traversing ephemeral stream channels with a laser-total station and used these data to calibrate and validate high-resolution, digital imagery. In addition, crucial geomorphic markers were dated by the
Seismotectonics of Northeastern Sicily and Southern Calabria (Italy): New constraints on the tectonic structures featuring in a crucial sector for the Central Mediterranean geodynamics

NASA Astrophysics Data System (ADS)

Scarfì, Luciano; Barberi, Graziella; Musumeci, Carla; Patanè, Domenico

2016-04-01

The purpose of this study is to gain a better understanding on the tectonic structures featuring in a crucial sector of central Mediterranean area, including the Aeolian Islands, southern Calabria and northeastern Sicily, where the convergence between Eurasian and African plates has given rise to a complicated collisional/subduction complex. A high quality dataset of about 3000 earthquakes has been exploited for local earthquake tomography and focal mechanisms computation. Results depict undiscovered details of a network of faults which enables the contemporary existence of adjacent compressional and extensional domains. In particular, tomographic images, seismic events distribution and focal mechanisms pinpoint the geometry and activity of a lithospheric-scale tear faults system which, with a NW-SE trend through Sicily and the Tyrrhenian and Ionian Seas, represents the southern edge of the Ionian subduction trench zone. At crustal depth, this tearing is well highlighted by a rotation of the maximum horizontal stress, moving across the area from west toward east. In addition, the shallow normal fault regime, characterising the northeastern Sicily mainland, south of the NW-SE lineament, changes in the deeper part of the crust. Indeed, a NE-SW earthquake distribution, NW gently dipping, and inverse fault solutions indicate a still active contractional deformation in the eastern Sicily, caused by the Africa-Eurasia convergence and well framed with the current compressive regime along the southern Tyrrhenian zone and at the front of the Sicilian Chain-Foreland.
Active tectonics in the Mygdonia basin (northern Greece): a combined seismological and remote-sensed geomorphology approach

NASA Astrophysics Data System (ADS)

Gkarlaouni, Charikleia; Andreani, Louis; Pennos, Chris; Gloaguen, Richard; Papadimitriou, Eleftheria; Kilias, Adamantios; Michail, Maria

2014-05-01

along the southern flank of the Mygdonia graben. Observed differences may be related to a diachronic evolution. River profiles crossing the Thessaloniki-Gerakarou fault system (TGFS) south of the Mygdonia basin display anomalies such as knickpoints or convex segments. These anomalies reflect significant changes in river base-levels possibly triggered by uplift/subsidence processes. We also computed the normalized steepness index (ksn) for concave segments in rivers. We observe an increase of ksn values towards the south while the lithology remains almost constant. These changes in ksn values may be thus related to an increase in deformation rates along the southern TGFS. Our geomorphic analysis also highlighted several flat paleo-surfaces located on top of main ranges at elevations comprised between 300 and 450m above the basin infill. Finally, we produced thematic maps combining present-day seismicity, historical earthquakes and geomorphic features derived from DEM. The combined use of both seismology and remote-sensed geomorphology allowed us to better understand the at-depth and surface expressions of active structures within the Mygdonia basin. It also provided further insights into the tectonic evolution of the study area. This project is funded by the German Academic Exchange Service (DAAD) and the Greek State Scholarschips Foundation (IKY) under the IKYDA initiative.
Extensional tectonics on continents and the transport of heat and matter

NASA Technical Reports Server (NTRS)

Neugebauer, H. J.

1985-01-01

Intracontinental zones of extensional tectonic style are commonly of finite width and length. Associated sedimentary troughs are fault-controlled. The evolution of those structures is accompanied by volcanic activity of variable intensity. The characteristic surface structures are usually underlaid by a lower crust of the transitional type while deeper subcustal areas show delayed travel times of seismic waves especially at young tectonic provinces. A correspondence between deep-seated processes and zones of continental extension appears obvious. A sequential order of mechanisms and their importance are discussed in the light of modern data compilations and quantitative kinematic and dynamic approaches. The Cenozoic exensional tectonics related with the Rhine River are discussed.
The Role of Long-Term Tectonic Deformation on the Distribution of Present-Day Seismic Activity in the Caribbean and Central America

NASA Astrophysics Data System (ADS)

Schobelock, J.; Stamps, D. S.; Pagani, M.; Garcia, J.; Styron, R. H.

2017-12-01

The Caribbean and Central America region (CCAR) undergoes the entire spectrum of earthquake types due to its complex tectonic setting comprised of transform zones, young oceanic spreading ridges, and subductions along its eastern and western boundaries. CCAR is, therefore, an ideal setting in which to study the impacts of long-term tectonic deformation on the distribution of present-day seismic activity. In this work, we develop a continuous tectonic strain rate model based on inter-seismic geodetic data and compare it with known active faults and earthquake focal mechanism data. We first create a 0.25o x 0.25o finite element mesh that is comprised of block geometries defined in previously studies. Second, we isolate and remove transient signals from the latest open access community velocity solution from UNAVCO, which includes 339 velocities from COCONet and TLALOCNet GNSS data for the Caribbean and Central America, respectively. In a third step we define zones of deformation and rigidity by creating a buffer around the boundary of each block that varies depending on the size of the block and the expected deformation zone based on locations of GNSS data that are consistent with rigid block motion. We then assign each node within the buffer a 0 for the deforming areas and a plate index outside the buffer for the rigid. Finally, we calculate a tectonic strain rate model for CCAR using the Haines and Holt finite element approach to fit bi-cubic Bessel splines to the the GNSS/GPS data assuming block rotation for zones of rigidity. Our model of the CCAR is consistent with compression along subduction zones, extension across the mid-Pacific Rise, and a combination of compression and extension across the North America - Caribbean plate boundary. The majority of CCAR strain rate magnitudes range from -60 to 60 nanostrains/yr. Modeling results are then used to calculate expected faulting behaviors that we compare with mapped geologic faults and seismic activity.
Formation of cratonic lithosphere during the initiation of plate tectonics

NASA Astrophysics Data System (ADS)

Moresi, L. N.; Beall, A.; Cooper, C. M.

2017-12-01

The Earth's oldest near-surface material, the cratonic crust, is typically underlain by unusually thick Archean lithosphere (<300 km). This cratonic lithosphere likely thickened in a high compressional stress environment. Mantle convection in the hotter Archean Earth would have imparted relatively low stresses on the lithosphere, whether or not tectonics was operating, so a high stress signal from the early Earth is paradoxical. We propose that a rapid transition, from a stagnant lid Earth to the onset of plate tectonics, generated the high stresses required to thicken the cratonic lithosphere. Numerical calculations are used to demonstrate that an existing buoyant and strong layer, representing harzburgite and felsic crust, can thicken and stabilize during the lid-breaking event. The peak compressional stress experienced by lithosphere is 3-4 higher than for the stagnant lid or mobile lid regimes immediately before and after. It is plausible that the cratonic lithosphere has still not returned to this high stress-state, explaining its stability. The lid-breaking thickening event reproduces craton features previously attributed to subduction: thrust structures, assembled crustal fragments and transport of basaltic upper crust to depths required to generate felsic melt. Palaeoarchean `pre-tectonic' structures can also survive the lid-breaking event, acting as strong crustal rafts. Together, the results indicate that the signature of a catastrophic switch, from a stagnant lid Earth to the initiation of plate tectonics, has been captured and preserved in the unusual characteristics of cratonic crust and lithosphere.
Tectonic characterization of a potential high-level nuclear waste repository at Yucca Mountain, Nevada

USGS Publications Warehouse

Whitney, John W.; O'Leary, Dennis W.

1993-01-01

Tectonic characterization of a potential high-level nuclear waste repository at Yucca Mountain, Nevada, is needed to assess seismic and possible volcanic hazards that could affect the site during the preclosure (next 100 years) and the behavior of the hydrologic system during the postclosure (the following 10,000 years) periods. Tectonic characterization is based on assembling mapped geological structures in their chronological order of development and activity, and interpreting their dynamic interrelationships. Addition of mechanistic models and kinematic explanations for the identified tectonic processes provides one or more tectonic models having predictive power. Proper evaluation and application of tectonic models can aid in seismic design and help anticipate probable occurrence of future geologic events of significance to the repository and its design.
Subduction controls the distribution and fragmentation of Earth’s tectonic plates.

PubMed

Mallard, Claire; Coltice, Nicolas; Seton, Maria; Müller, R Dietmar; Tackley, Paul J

2016-07-07

The theory of plate tectonics describes how the surface of Earth is split into an organized jigsaw of seven large plates of similar sizes and a population of smaller plates whose areas follow a fractal distribution. The reconstruction of global tectonics during the past 200 million years suggests that this layout is probably a long-term feature of Earth, but the forces governing it are unknown. Previous studies, primarily based on the statistical properties of plate distributions, were unable to resolve how the size of the plates is determined by the properties of the lithosphere and the underlying mantle convection. Here we demonstrate that the plate layout of Earth is produced by a dynamic feedback between mantle convection and the strength of the lithosphere. Using three-dimensional spherical models of mantle convection that self-consistently produce the plate size–frequency distribution observed for Earth, we show that subduction geometry drives the tectonic fragmentation that generates plates. The spacing between the slabs controls the layout of large plates, and the stresses caused by the bending of trenches break plates into smaller fragments. Our results explain why the fast evolution in small back-arc plates reflects the marked changes in plate motions during times of major reorganizations. Our study opens the way to using convection simulations with plate-like behaviour to unravel how global tectonics and mantle convection are dynamically connected.
Topographic Comparisons of Uplift Features on Venus and Earth

NASA Astrophysics Data System (ADS)

Stoddard, P. R.; Jurdy, D. M.

2009-12-01

Earth and Venus, nearly twins, have very different resurfacing histories. Like the Earth, Venus has a global rift system, often cited as evidence of tectonic activity, despite the apparent lack of Earth-style plate tectonics. Both systems are marked by large ridges, usually with central grabens. On Earth, the topography of the rifts can be modeled well by a cooling half-space and the spreading of two divergent plates. The origin of the topographic signature on Venus, however, remains enigmatic. Venus and Earth also both have regions of apparent upwelling: hotspots on Earth, and regiones on Venus. Both are marked by broad topographic and geoid highs as well as evidence of volcanic activity. We use topographic profiles to compare well-understood terrestrial analogs to venusian features. Specifically, we cross-correlate average profiles for terrestrial rifts (slow, fast, incipient and extinct) and hotspots (oceanic and continental) with those for venusian chasmata and regiones. We perform a principal component analysis to objectively assess degrees of similarity and differences to draw inferences as to the processes responsible for shaping Venus' surface. We analyze profiles of the Labrador Ridge, East African Rift, slow-spreading Mid-Atlantic Ridge and the fast-spreading East Pacific Rise for comparison with profiles for several venusian chasmata in different settings. For upwelling regions, we look at the Hawaii, Iceland, Reunion, and Yellowstone hotspots and Atla, Beta, and W. Eistla regiones on Venus. For ridge features, we take profiles perpendicular to the ridge trend every half-degree or so. For uplift features, we take 36 radial profiles through the center of the feature at 10 degree intervals. We use profiles from 800 to 1200 km long. For each feature, we average all profiles, then cross-correlate the individual profiles with the resulting average. Next, we cross-correlate the average profiles of each feature with those of the other features. Thus we obtain a
Three sets of crystallographic sub-planar structures in quartz formed by tectonic deformation

NASA Astrophysics Data System (ADS)

Derez, Tine; Pennock, Gill; Drury, Martyn; Sintubin, Manuel

2016-05-01

In quartz, multiple sets of fine planar deformation microstructures that have specific crystallographic orientations parallel to planes with low Miller-Bravais indices are commonly considered as shock-induced planar deformation features (PDFs) diagnostic of shock metamorphism. Using polarized light microscopy, we demonstrate that up to three sets of tectonically induced sub-planar fine extinction bands (FEBs), sub-parallel to the basal, γ, ω, and π crystallographic planes, are common in vein quartz in low-grade tectonometamorphic settings. We conclude that the observation of multiple (2-3) sets of fine scale, closely spaced, crystallographically controlled, sub-planar microstructures is not sufficient to unambiguously distinguish PDFs from tectonic FEBs.
Interaction between central volcanoes and regional tectonics along divergent plate boundaries: Askja, Iceland

NASA Astrophysics Data System (ADS)

Trippanera, Daniele; Ruch, Joël; Acocella, Valerio; Thordarson, Thor; Urbani, Stefano

2018-01-01

Activity within magmatic divergent plate boundaries (MDPB) focuses along both regional fissure swarms and central volcanoes. An ideal place to investigate their mutual relationship is the Askja central volcano in Iceland. Askja consists of three nested calderas (namely Kollur, Askja and Öskjuvatn) located within a hyaloclastite massif along the NNE-SSW trending Icelandic MDPB. We performed an extensive field-based structural analysis supported by a remote sensing study of tectonic and volcanic features of Askja's calderas and of the eastern flank of the hyaloclastite massif. In the massif, volcano-tectonic structures trend N 10° E to N 40° E, but they vary around the Askja caldera being both parallel to the caldera rim and cross-cutting on the Western side. Structural trends around the Öskjuvatn caldera are typically rim parallel. Volcanic vents and dikes are preferentially distributed along the caldera ring faults; however, they follow the NNE-SSW regional structures when located outside the calderas. Our results highlight that the Askja volcano displays a balanced amount of regional (fissure-swarm related) and local (shallow-magma-chamber related) tectonic structures along with a mutual interaction among these. This is different from Krafla volcano (to the north of Askja) dominated by regional structures and Grímsvötn (to the South) dominated by local structures. Therefore, Askja represents an intermediate tectono-magmatic setting for volcanoes located in a slow divergent plate boundary. This is also likely in accordance with a northward increase in the spreading rate along the Icelandic MDPB.
Is Active Tectonics on Madagascar Consistent with Somalian Plate Kinematics?

NASA Astrophysics Data System (ADS)

Stamps, D. S.; Kreemer, C.; Rajaonarison, T. A.

2017-12-01

The East African Rift System (EARS) actively breaks apart the Nubian and Somalian tectonic plates. Madagascar finds itself at the easternmost boundary of the EARS, between the Rovuma block, Lwandle plate, and the Somalian plate. Earthquake focal mechanisms and N-S oriented fault structures on the continental island suggest that Madagascar is experiencing east-west oriented extension. However, some previous plate kinematic studies indicate minor compressional strains across Madagascar. This inconsistency may be due to uncertainties in Somalian plate rotation. Past estimates of the rotation of the Somalian plate suffered from a poor coverage of GPS stations, but some important new stations are now available for a re-evaluation. In this work, we revise the kinematics of the Somalian plate. We first calculate a new GPS velocity solution and perform block kinematic modeling to evaluate the Somalian plate rotation. We then estimate new Somalia-Rovuma and Somalia-Lwandle relative motions across Madagascar and evaluate whether they are consistent with GPS measurements made on the island itself, as well as with other kinematic indicators.
The Investigation of Active Tectonism Offshore Cide-Sinop, Southern Black Sea by Seismic Reflection and Bathymetric Data

NASA Astrophysics Data System (ADS)

Alp, Y. I.; Ocakoglu, N.; Kılıc, F.; Ozel, A. O.

2017-12-01

The active tectonism offshore Cide-Sinop at the Southern Black Sea shelf area was first time investigated by multi-beam bathymetric and multi-channel seismic reflection data under the Research Project of The Scientific and Technological Research Council of Turkey (TUBİTAK-ÇAYDAG-114Y057). The multi-channel seismic reflection data of about 700 km length were acquired in 1991 by Turkish Petroleum Company (TP). Multibeam bathymetric data were collected between 2002-2008 by the Turkish Navy, Department of Navigation, Hydrography and Oceanography (TN-DNHO). Conventional data processing steps were applied as follows: in-line geometry definition, shot-receiver static correction, editing, shot muting, gain correction, CDP sorting, velocity analysis, NMO correction, muting, stacking, predictive deconvolution, band-pass filtering, finite-difference time migration, and automatic gain correction. Offshore area is represented by a quite smooth and large shelf plain with an approx. 25 km wide and the water depth of about -100 m. The shelf gently deepens and it is limited by the shelf break with average of -120 m contour. The seafloor morphology is charasterised by an erosional surface. Structurally, E-W trending strike-slip faults with generally compression components and reverse/thrust faults have been regionally mapped for the first time. Most of these faults deform all seismic units and reach the seafloor delimiting the morphological highs and submarine plains. Thus, these faults are intepreted as active faults. These results support the idea that the area is under the active compressional tectonic regime
Ogaden Basin subsidence history: Another key to the Red Sea-Gulf of Aden tectonic puzzle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pigott, J.D.; Neese, D.; Carsten, G.

1995-08-01

Previous work has attempted to understand the tectonic evolution of the Red Sea-Gulf of Aden region through a focus upon plate kinematics and reconstruction of plate interactions in a two dimensional sense. A significant complement to the three dimensional puzzle can be derived from a critical examination of the vertical component, tectonic subsidence analysis. By removing the isostatic contributions of sediment loading and unloading, and fluctuations in sea level, the remaining thermal-mechanical contribution to a basin`s subsidence can be determined. Such an analysis of several Ogaden Basin wells reveals multiple pulses of tectonic subsidence and uplift which correspond to far-fieldmore » tectonic activities in the Red Sea and Gulf of Aden. One of the more dramatic is a Jurassic tectonic pulse circa 145-130 m.a., and a later extensional event which correlates to a major subsidence event ubiquitous through-out the Gulf of Aden, related to Gondwana Land breakup activities. Tectonic uplift during the Tertiary coincides with early Red Sea rifting episodes. Such activities suggest the Ogaden Basin has been a relatively stable East African cratonic basin, but with heating-extension events related to nearby plate interactions. In terms of hydrocarbon generation, the use of steady state present day geothermal gradients, coupled with subsidence analysis shows that potential Paleozoic and Mesozoic source rocks initiated generation as early as the Jurassic. The generating potential of Paleozoic source rocks would only be exacerbated by later heating events. Furthermore, cooling and tectonic uplift during the Tertiary would tend to arrest on-going hydrocarbon generation for Jurassic source rocks in the Ogaden area.« less

Tectonic resurfacing of Venus

NASA Technical Reports Server (NTRS)

Malin, Michael C.; Grimm, Robert E.; Herrick, Robert R.

1993-01-01

Impact crater distributions and morphologies have traditionally played an important role in unraveling the geologic histories of terrestrial objects, and Venus has proved no exception. The key observations are: mean crater retention age about 500 Ma; apparently random spatial distribution; modest proportion (17 percent) of modified craters; and preferential association of modified craters with areas of low crater density. The simplest interpretation of these data alone is that Venus experienced global resurfacing (assumed to be largely volcanic) prior to 500 Ma, after which time resurfacing rates decreased dramatically. This scenario does not totally exclude present geological activity: some resurfacing and crater obliteration is occurring on part of the planet, but at rates much smaller than on Earth. An alternative endmember model holds that resurfacing is also spatially randomly distributed. Resurfacing of about 1 sq km/yr eliminates craters such that a typical portion of the surface has an age of 500 Ma, but actual ages range from zero to about 1000 Ma. Monte Carlo simulation indicates that the typical resurfacing 'patch' cannot exceed about 500 km in diameter without producing a crater distribution more heterogeneous than observed. Volcanic or tectonic processes within these patches must be locally intense to be able to obliterate craters completely and leave few modified. In this abstract, we describe how global geologic mapping may be used to test resurfacing hypotheses. We present preliminary evidence that the dominant mode of resurfacing on Venus is tectonism, not volcanism, and that this process must be ongoing today. Lastly, we outline a conceptual model in which to understand the relationship between global tectonics and crater distribution and preservation.
Episodic plate tectonics on Venus

NASA Technical Reports Server (NTRS)

Turcotte, Donald

1992-01-01

Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.
Breaking rocks made easy: subcritical processes and tectonic predesign

NASA Astrophysics Data System (ADS)

Voigtlaender, Anne; Krautblatter, Michael

2017-04-01

In geomorphic studies, to change in landforms, e.g. by rock slope failure, fluvial or glacial erosion, a threshold is commonly assumed, which is crossed either by an increase in external driving or a decrease of internal resisting forces, respectively. If the threshold is crossed, bedrock breaks and slope fails, rivers incise and glaciers plug and sew their bed. Here we put forward a focus on the decrease of the resisting forces, as an increase in the driving forces, to match the strength of bedrock, is not that likely. We suggest that the degradation of resisting forces of bedrock can be better explained by subcritical processes like creep, fatigue and stress corrosion interplaying with tectonic predesign. Both concepts, subcritical processes and tectonic predesign have been issued in the last century, but have not been widely accepted nor have their assumptions been explicitly stressed in recent case studies. Moreover both concepts profit especially on scale issues if merged. Subcritical crack growth, includes different mechanisms promoting fractures well below the ultimate strength. Single infinitesimal but irreversible damage and deformations are induced in the material over time. They interact with inherent microstructural flaws and low applied stresses, limiting local strength and macroscopic behavior of bedrock. This reissues the concept of tectonic predesigned, as proposed by A.E. Scheidegger, which not only encompasses structural features that determine the routing of drainage patterns and shear planes, e.g. joints, faults and foliations, but also the (neo)tectonic stress-field and the (in-situ) strain state of bedrocks and mountains. Combining subcritical processes and tectonic predesign we can better explain, why and where we see a dissected, eroded and geomorphic divers' landscape. In this conceptual framework actual magnitudes of the driving forces are accounted for and so is the nature of the bedrock material, to better understand the trajectories of
Earthquakes and plate tectonics

USGS Publications Warehouse

Spall, H.

1977-01-01

An explanation is to be found in plate tectonics, a concept which has revolutionized thinking in the Earth sciences in the last 10 years. The theory of plate tectonics combines many of the ideas about continental drift (originally proposed in 1912 by Alfred Wegener in Germany) and sea-floor spreading (suggested originally by Harry Hess of Princeton University).
Magmatic versus tectonic influence in the Eolian arc: the case of Vulcano and Lipari islands revisited

NASA Astrophysics Data System (ADS)

Ruch, Joel; Di Lorenzo, Riccardo; Vezzoli, Luigina Maria; De Rosa, Rosanna; Acocella, Valerio; Catalano, Stefano; Romagnoli, Gino

2014-05-01

The prevalent influence of magma versus tectonics for the edification and the evolution of volcanic zones is matter of debate. Here we focus on Vulcano and Lipari, two active volcanic islands located in the central sector of the Eolian arc (North of Sicily). Both systems are influenced by regional tectonics and affected by historical magmatic events taking place along a NS oriented structure, connecting both islands. We revisit and implement previous structural studies performed during the 1980's considering several new geophysical, geochemical and geodynamical findings. Four extensive structural campaigns have been performed on both islands and along the shorelines in 2012-2013 covering about 80% of the possible accessible outcrops. We collected ~500 measurements (e.g. faults, fractures and dikes) at 40 sites. Overall, most of the observed structures are oriented N-S and NNW-SSE, confirming previous studies, however, almost all features are strikingly dominated by an EW-oriented extensive regime, which is a novelty. These findings are supported by kinematic indicators and suggest a predominant dip-slip component (pitch from 80 and 130°) with alternating left and right kinematics. Marginal faulting in most recent formations have been observed, suggesting that the deformation may occur preferentially during transient deformation related to periods of magmatic activity, instead of resulting from continuous regional tectonic processes. Overall, fault and dike planes are characterized by a dominant eastward immersion, suggesting an asymmetric graben-like structure of the entire area. This may be explained by the presence of a topographic gradient connecting both islands to the deep Gioia basin to the East, leading to a preferential ample gravitational collapse. Finally, we propose a model in which the stress field rotates northward. It transits from a pure right lateral strike-slip regime along the Tindari fault zone (tectonic-dominant) to an extensive regime
A detection method of subrecent to recent tectonic activity in the anticlinal system of the northern Negev, Israel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zilberman, E.; Wachs, D.

Geomorphological and geophysical methods combined with borehole information were employed to search for possible subrecent small-scale vertical movement along the anticlinal fold belt of the central Negev, Israel. Such tectonic deformation might indicate displacement on the buried reverse faults underneath the anticlines. Variations in the thickness of the alluvial fill in the study area, which are in accordance with the fold structures, could be an indication of recent folding activity along the anticlinal system. In order to detect these thickness variations in the alluvial fill, seismic refraction and electrical resistivity measurements were carries out along the valley of Nahal Besor,more » which crosses the anticlinal belt. The thickness variations of the alluvial fill along the valley were not found to indicate any significant tectonic movement along the anticlines during the Pleistocene. The thickest alluvium was found overlying a karst bedrock, hence karst relief is suggested to be responsible for these variations.« less
Gravity anomalies and associated tectonic features over the Indian Peninsular Shield and adjoining ocean basins

NASA Astrophysics Data System (ADS)

Mishra, D. C.; Arora, K.; Tiwari, V. M.

2004-02-01

A combined gravity map over the Indian Peninsular Shield (IPS) and adjoining oceans brings out well the inter-relationships between the older tectonic features of the continent and the adjoining younger oceanic features. The NW-SE, NE-SW and N-S Precambrian trends of the IPS are reflected in the structural trends of the Arabian Sea and the Bay of Bengal suggesting their probable reactivation. The Simple Bouguer anomaly map shows consistent increase in gravity value from the continent to the deep ocean basins, which is attributed to isostatic compensation due to variations in the crustal thickness. A crustal density model computed along a profile across this region suggests a thick crust of 35-40 km under the continent, which reduces to 22/20-24 km under the Bay of Bengal with thick sediments of 8-10 km underlain by crustal layers of density 2720 and 2900/2840 kg/m 3. Large crustal thickness and trends of the gravity anomalies may suggest a transitional crust in the Bay of Bengal up to 150-200 km from the east coast. The crustal thickness under the Laxmi ridge and east of it in the Arabian Sea is 20 and 14 km, respectively, with 5-6 km thick Tertiary and Mesozoic sediments separated by a thin layer of Deccan Trap. Crustal layers of densities 2750 and 2950 kg/m 3 underlie sediments. The crustal density model in this part of the Arabian Sea (east of Laxmi ridge) and the structural trends similar to the Indian Peninsular Shield suggest a continent-ocean transitional crust (COTC). The COTC may represent down dropped and submerged parts of the Indian crust evolved at the time of break-up along the west coast of India and passage of Reunion hotspot over India during late Cretaceous. The crustal model under this part also shows an underplated lower crust and a low density upper mantle, extending over the continent across the west coast of India, which appears to be related to the Deccan volcanism. The crustal thickness under the western Arabian Sea (west of the Laxmi ridge
Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eisses, A.; Kell, A.; Kent, G.

Amy Eisses, Annie M. Kell, Graham Kent, Neal W. Driscoll, Robert E. Karlin, Robert L. Baskin, John N. Louie, Kenneth D. Smith, Sathish Pullammanappallil, 2011, Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada: presented at American Geophysical Union Fall Meeting, San Francisco, Dec. 5-9, abstract NS14A-08.
Seismotectonics of northeastern Sicily and southern Calabria (Italy): New constraints on the tectonic structures featuring in a crucial sector for the central Mediterranean geodynamics

NASA Astrophysics Data System (ADS)

Scarfı, L.; Barberi, G.; Musumeci, C.; Patanè, D.

2016-03-01

The purpose of this study is to gain a better understanding on the tectonic structures featuring in a crucial sector of central Mediterranean area, including the Aeolian Islands, southern Calabria, and northeastern Sicily, where the convergence between Eurasian and African Plates has given rise to a complicated collisional/subduction complex. A high-quality data set of about 3000 earthquakes has been exploited for local earthquake tomography and focal mechanisms computation together with available source mechanisms from published catalogues. The results depict new details of a network of faults which enables the concurrent existence of adjacent compressional and extensional domains. In particular, tomographic images, seismic events distribution, and focal mechanisms pinpoint the geometry and activity of a lithospheric-scale tear faults system which, with a NW-SE trend through Sicily and the Tyrrhenian and Ionian Seas, represents the southern edge of the Ionian subduction trench zone. At crustal depth, this tearing is well highlighted by a rotation of the maximum horizontal stress, moving across the area from west toward east. In addition, the shallow normal fault regime, characterizing the southern Calabria and northeastern Sicily mainland, south of the NW-SE lineament, changes in the deeper part of the crust. Indeed, a NE-SW earthquake distribution, gently dipping NW, and inverse fault solutions indicate a still active contractional deformation in eastern Sicily, caused by the Africa-Eurasia convergence and well framed with the current compressive regime along the southern Tyrrhenian zone and at the front of the Sicilian Chain-Foreland.
Block Tectonic Motion on Venus

NASA Astrophysics Data System (ADS)

Byrne, P. K.; Ghail, R.; Sengor, A. M. C.; Klimczak, C.; Solomon, S. C.

2017-12-01

Despite close similarities in mass and bulk composition to Earth, Venus apparently shows no evidence for Earth-like plate tectonics, except perhaps for limited plume-induced subduction. We use Magellan radar data to survey numerous examples of low-lying areas infilled with plains lavas and delimited by networks of narrow belts of substantial tectonic deformation; such sites include those at Lavinia and Llorona Planitiæ and to the north of Helen Planitia. This deformation is locally extensional or shortening in style but very often also includes structures that denote substantial lateral motion. Cross-cutting relations suggest that this motion occurred both before and after the lavas were emplaced. Together, these observations imply that many of the belt-bounded areas have acted as relatively rigid blocks that experienced considerable horizontal movement relative to each other, in a manner similar to blocks that constitute parts of the Terran continental lithosphere. On Earth, continental deformation is enabled by the low strength of the lower crust and/or upper mantle. On Venus, the shallow brittle-ductile transition (BDT), a result of the planet's elevated surface temperature, likely acts in a similar way to decouple the upper and lower crust. Subcrustal lid rejuvenation, a recently proposed mechanism for renewal of the mantle portion of Venus' stagnant lithospheric lid through thinning and recycling, could drive the horizontal movement of these rigid blocks. It may be, then, that the blocks move as continental blocks do on Earth, with mantle motion transferred to the surface and manifest as narrow zones of tectonic deformation akin to, for example, the Tian Shan and Altin Tagh ranges that bound the Tarim Basin in northwestern China. The shallow BDT on Venus precludes the blocks from subducting, and so their fate is to shorten, lengthen, or retain their geometry at the expense of adjacent blocks. We suggest that this behavior is analogous to plate-tectonic
Structural-tectonic zoning of the Arctic

NASA Astrophysics Data System (ADS)

Petrov, Oleg; Sobolev, Nikolay; Morozov, Andrey; Shokalsky, Sergey; Kashubin, Sergey; Grikurov, Garrik; Tolmacheva, Tatiana; Rekant, Pavel; Petrov, Evgeny

2017-04-01

Structural-tectonic zoning of the Arctic is based on the processing of geological and geophysical data and bottom sampling materials produced within the project "Atlas of Geological Maps of the Circumpolar Arctic." Zoning of the Arctic territories has been conducted taking into account the Earth's crust types, age of consolidated basement, and features of geological structure of the sedimentary cover. Developed legend for the zoning scheme incorporates five main groups of elements: continental and oceanic crust, folded platform covers, accretion-collision systems, and provinces of continental cover basalts. An important feature of the structural-tectonic zoning scheme is designation of continental crust in the central regions of the Arctic Ocean, the existence of which is assumed on the basis of numerous geological data. It has been found that most of the Arctic region has continental crust with the exception of the Eurasian Basin and the central part of the Canada Basin, which are characterized by oceanic crust type. Thickness of continental crust from seismic data varies widely: from 30-32 km on the Mendeleev Rise to 18-20 km on the Lomonosov Ridge, decreasing to 8-10 km in rift structures of the Podvodnikov-Makarov Basin at the expense of reduction of the upper granite layer. New data confirm similar basement structure on the western and eastern continental margins of the Eurasian oceanic basin. South to north, areas of Neoproterozoic (Baikalian) and Paleozoic (Ellesmerian) folding are successively distinguished. Neoproterozoic foldbelt is observed in Central Taimyr (Byrranga Mountains). Continuation of this belt in the eastern part of the Arctic is Novosibirsk-Chukchi fold system. Ellesmerian orogen incorporates the northernmost areas of Taimyr and Severnaya Zemlya, wherefrom it can be traced to the Geofizikov Spur of the Lomonosov Ridge and further across the De Long Archipelago and North Chukchi Basin to the north of Alaska Peninsula and in the Beaufort Sea
Subsidence of the South Polar Terrain and global tectonic of Enceladus

NASA Astrophysics Data System (ADS)

Czechowski, Leszek

2016-04-01

compressional surface features do not have to be dominant. The SPT is compressed, so "tiger stripes" could exist for long time. Only after significant subsidence (below 1200 m) the regime of stresses changes to compressional. We suppose that it means the end of activity in a given region. Acknowledgments This work was partially supported by the National Science Centre (grant 2011/01/B/ST10/06653). Computer resources of Interdisciplinary Centre for Mathematical and Computational Modeling of University of Warsaw were also used in the research References [1] Spencer, J. R., et al. (2009) Enceladus: An Active Cryovolcanic Satellite, in: M.K. Dougherty et al. (eds.), Saturn from Cassini-Huygens, Springer Science, p. 683. [2] Czechowski L. (2015) Mass loss as a driving mechanism of tectonics of Enceladus 46th Lunar and Planetary Science Conference 2030.pdf. [3] Czechowski, L., (2014) Some remarks on the early evolution of Enceladus. Planet. Sp. Sc. 104, 185-199.
Global evaluation of erosion rates in relation to tectonics

NASA Astrophysics Data System (ADS)

Hecht, Hagar; Oguchi, Takashi

2017-12-01

Understanding the mechanisms and controlling factors of erosion rates is essential in order to sufficiently comprehend bigger processes such as landscape evolution. For decades, scientists have been researching erosion rates where one of the main objectives was to find the controlling factors. A variety of parameters have been suggested ranging from climate-related, basin morphometry and the tectonic setting of an area. This study focuses on the latter. We use previously published erosion rate data obtained mainly using 10Be and sediment yield and sediment yield data published by the United States Geological Survey. We correlate these data to tectonic-related factors, i.e., distance to tectonic plate boundary, peak ground acceleration ( PGA), and fault distribution. We also examine the relationship between erosion rate and mean basin slope and find significant correlations of erosion rates with distance to tectonic plate boundary, PGA, and slope. The data are binned into high, medium, and low values of each of these parameters and grouped in all combinations. We find that groups with a combination of high PGA (> 0.2.86 g) and long distance (> 1118.69 km) or low PGA (< 0.68 g) and short distance (< 94.34 km) are almost inexistent suggesting a strong coupling between PGA and distance to tectonic plate boundary. Groups with low erosion rates include long distance and/or low PGA, and groups with high erosion rates include neither of these. These observations indicate that tectonics plays a major role in determining erosion rates, which is partly ascribable to steeper slopes produced by active crustal movements. However, our results show no apparent correlation of slope with erosion rates, pointing to problems with using mean basin-wide slope as a slope indicator because it does not represent the complex slope distribution within a basin.
GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany).

PubMed

Berberich, Gabriele; Schreiber, Ulrich

2013-05-17

In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel.
Surface features of central North America: a synoptic view from computer graphics

USGS Publications Warehouse

Pike, R.J.

1991-01-01

A digital shaded-relief image of the 48 contiguous United States shows the details of large- and small-scale landforms, including several linear trends. The features faithfully reflect tectonism, continental glaciation, fluvial activity, volcanism, and other surface-shaping events and processes. The new map not only depicts topography accurately and in its true complexity, but does so in one synoptic view that provides a regional context for geologic analysis unobscured by clouds, culture, vegetation, or artistic constraints. -Author
Regional geology and tectonics

USGS Publications Warehouse

Nokleberg, Warren J.; Bundtzen, Thomas K.; Nokleberg, Warren J.; Price, Raymond A.; Scholl, David W.; Stone, David B.

2017-01-01

This chapter describes the regional geology and tectonic origins of the major geologic units for the Northern Cordillera. The goals of the chapter are to: (1) provide a summary and regional overview of this vast region that contains a complicated geologic history; and (2) describe the major geologic units and tectonic events that cover a broad geologic time span from the Proterozoic to the Holocene (Recent).
Andean tectonics: Implications for Satellite Geodesy

NASA Technical Reports Server (NTRS)

Allenby, R. J.

1984-01-01

Current knowledge and theories of large scale Andean tectonics as they relate to site planning for the NASA Crustal Dynamics Program's proposed high precision geodetic measurements of relative motions between the Nazca and South American plates are summarized. The Nazca Plate and its eastern margin, the Peru-Chile Trench, is considered a prototype plate marked by rapid motion, strong seismicity and well defined boundaries. Tectonic activity across the Andes results from the Nazca Plate subducting under the South American plate in a series of discrete platelets with different widths and dip angles. This in turn, is reflected in the tectonic complexity of the Andes which are a multitutde of orogenic belts superimposed on each other since the Precambrian. Sites for Crustal Dynamics Program measurements are being located to investigate both interplate and extraplate motions. Observing operations have already been initiated at Arequipa, Peru and Easter Island, Santiago and Cerro Tololo, Chile. Sites under consideration include Iquique, Chile; Oruro and Santa Cruz, Bolivia; Cuzco, Lima, Huancayo and Bayovar, Peru; and Quito and the Galapagos Islands, Ecuador. Based on scientific considerations, Santa Cruz, Huancayo (or Lima), Quito and the Galapagos Islands should be replaced by Isla San Felix, Chile; Brazilia or Petrolina, Brazil; and Guayaquil, Ecuador. If resources permit, additional important sites would be Buenaventura and Villavicencio or Puerto La Concordia, Colombia; and Mendoza and Cordoba, Argentina.
Identifying tectonic parameters that influence tsunamigenesis

NASA Astrophysics Data System (ADS)

van Zelst, Iris; Brizzi, Silvia; van Dinther, Ylona; Heuret, Arnauld; Funiciello, Francesca

2017-04-01

The role of tectonics in tsunami generation is at present poorly understood. However, the fact that some regions produce more tsunamis than others indicates that tectonics could influence tsunamigenesis. Here, we complement a global earthquake database that contains geometrical, mechanical, and seismicity parameters of subduction zones with tsunami data. We statistically analyse the database to identify the tectonic parameters that affect tsunamigenesis. The Pearson's product-moment correlation coefficients reveal high positive correlations of 0.65 between, amongst others, the maximum water height of tsunamis and the seismic coupling in a subduction zone. However, these correlations are mainly caused by outliers. The Spearman's rank correlation coefficient results in more robust correlations of 0.60 between the number of tsunamis in a subduction zone and subduction velocity (positive correlation) and the sediment thickness at the trench (negative correlation). Interestingly, there is a positive correlation between the latter and tsunami magnitude. In an effort towards multivariate statistics, a binary decision tree analysis is conducted with one variable. However, this shows that the amount of data is too scarce. To complement this limited amount of data and to assess physical causality of the tectonic parameters with regard to tsunamigenesis, we conduct a numerical study of the most promising parameters using a geodynamic seismic cycle model. We show that an increase in sediment thickness on the subducting plate results in a shift in seismic activity from outerrise normal faults to splay faults. We also show that the splay fault is the preferred rupture path for a strongly velocity strengthening friction regime in the shallow part of the subduction zone, which increases the tsunamigenic potential. A larger updip limit of the seismogenic zone results in larger vertical surface displacement.
Plate Tectonics: A Paradigm under Threat.

ERIC Educational Resources Information Center

Pratt, David

2000-01-01

Discusses the challenges confronting plate tectonics. Presents evidence that contradicts continental drift, seafloor spreading, and subduction. Reviews problems posed by vertical tectonic movements. (Contains 242 references.) (DDR)
Active transportation safety features around schools in Canada.

PubMed

Pinkerton, Bryn; Rosu, Andrei; Janssen, Ian; Pickett, William

2013-10-31

The purpose of this study was to describe the presence and quality of active transportation safety features in Canadian school environments that relate to pedestrian and bicycle safety. Variations in these features and associated traffic concerns as perceived by school administrators were examined by geographic status and school type. The study was based on schools that participated in 2009/2010 Health Behaviour in School-aged Children (HBSC) survey. ArcGIS software version 10 and Google Earth were used to assess the presence and quality of ten different active transportation safety features. Findings suggest that there are crosswalks and good sidewalk coverage in the environments surrounding most Canadian schools, but a dearth of bicycle lanes and other traffic calming measures (e.g., speed bumps, traffic chokers). Significant urban/rural inequities exist with a greater prevalence of sidewalk coverage, crosswalks, traffic medians, and speed bumps in urban areas. With the exception of bicycle lanes, the active transportation safety features that were present were generally rated as high quality. Traffic was more of a concern to administrators in urban areas. This study provides novel information about active transportation safety features in Canadian school environments. This information could help guide public health efforts aimed at increasing active transportation levels while simultaneously decreasing active transportation injuries.

Active Transportation Safety Features around Schools in Canada

PubMed Central

Pinkerton, Bryn; Rosu, Andrei; Janssen, Ian; Pickett, William

2013-01-01

The purpose of this study was to describe the presence and quality of active transportation safety features in Canadian school environments that relate to pedestrian and bicycle safety. Variations in these features and associated traffic concerns as perceived by school administrators were examined by geographic status and school type. The study was based on schools that participated in 2009/2010 Health Behaviour in School-aged Children (HBSC) survey. ArcGIS software version 10 and Google Earth were used to assess the presence and quality of ten different active transportation safety features. Findings suggest that there are crosswalks and good sidewalk coverage in the environments surrounding most Canadian schools, but a dearth of bicycle lanes and other traffic calming measures (e.g., speed bumps, traffic chokers). Significant urban/rural inequities exist with a greater prevalence of sidewalk coverage, crosswalks, traffic medians, and speed bumps in urban areas. With the exception of bicycle lanes, the active transportation safety features that were present were generally rated as high quality. Traffic was more of a concern to administrators in urban areas. This study provides novel information about active transportation safety features in Canadian school environments. This information could help guide public health efforts aimed at increasing active transportation levels while simultaneously decreasing active transportation injuries. PMID:24185844
Sedimentary record of seismic events in the Eocene Green River Formation and its implications for regional tectonics on lake evolution (Bridger Basin, Wyoming)

NASA Astrophysics Data System (ADS)

Törő, Balázs; Pratt, Brian R.

2016-10-01

, underfilled Wilkins Peak Member. Thus, these seismites are evidence for regional-scale changes in lacustrine sedimentation of Eocene Lake Gosiute in response to syndepositional tectonic activity. Analysis of synsedimentary deformation features is, therefore, a promising yet under-utilized tool to trace the tectonic evolution of lacustrine deposits of the Green River Formation and other tectonically active marine and non-marine basins.
Introduction to Regional Geology, Tectonics, and Metallogenesis of Northeast Asia

USGS Publications Warehouse

Parfenov, Leonid M.; Badarch, Gombosuren; Berzin, Nikolai A.; Hwang, Duk-Hwan; Khanchuk, Alexander I.; Kuzmin, Mikhail I.; Nokleberg, Warren J.; Obolenskiy, Alexander O.; Ogasawara, Masatsugu; Prokopiev, Andrei V.; Rodionov, Sergey M.; Smelov, Alexander P.; Yan, Hongquan

2007-01-01

This introduction presents an overview of the regional geology, tectonics, and metallogenesis of Northeast Asia. The major purposes are to provide a relatively short summary of these features for readers who are unfamiliar with Northeast Asia; a general scientific introduction for the succeeding chapters of this volume; and an overview of the methodology of metallogenic and tectonic analysis employed for Northeast Asia. The introduction also describes how a high-quality metallogenic and tectonic analysis, including synthesis of an associated metallogenic-tectonic model will greatly benefit refinement of mineral deposit models and deposit genesis; improvement of assessments of undiscovered mineral resources as part of quantitative mineral resource assessment studies; land-use and mineral exploration planning; improvement of interpretations of the origins of host rocks, mineral deposits, and metallogenic belts; and suggestions for new research. The compilation, synthesis, description, and interpretation of metallogenesis and tectonics of major regions, such as Northeast Asia (Eastern Russia, Mongolia, northern China, South Korea, and Japan) and the Circum-North Pacific (Russian Far East, Alaska, and Canadian Cordillera) requires a complex methodology. The methodology includes: (1) definitions of key terms; (2) compilation of a regional geologic base map that can be interpreted according to modern tectonic concepts and definitions; (3) compilation of a mineral deposit database that enables the determination of mineral deposit models, and relations of deposits to host rocks and tectonic origins; (4) synthesis of a series of mineral deposit models that characterize the known mineral deposits and inferred undiscovered deposits of the region; (5) compilation of a series of maps of metallogenic belts constructed on the regional geologic base map; and (6) formulation of a unified metallogenic and tectonic model. The summary of regional geology and metallogenesis in this
Active transpressional tectonics in the Andean forearc of southern Peru quantified by 10Be surface exposure dating of an active fault scarp

NASA Astrophysics Data System (ADS)

Benavente, Carlos; Zerathe, Swann; Audin, Laurence; Hall, Sarah R.; Robert, Xavier; Delgado, Fabrizio; Carcaillet, Julien; Team, Aster

2017-09-01

Our understanding of the style and rate of Quaternary tectonic deformation in the forearc of the Central Andes is hampered by a lack of field observations and constraints on neotectonic structures. Here we present a detailed analysis of the Purgatorio fault, a recently recognized active fault located in the forearc of southern Peru. Based on field and remote sensing analysis (Pléiades DEM), we define the Purgatorio fault as a subvertical structure trending NW-SE to W-E along its 60 km length, connecting, on its eastern end, to the crustal Incapuquio Fault System. The Purgatorio fault accommodates right-lateral transpressional deformation, as shown by the numerous lateral and vertical plurimetric offsets recorded along strike. In particular, scarp with a 5 m cumulative throw is preserved and displays cobbles that are cut and covered by slickensides. Cosmogenic radionuclide exposure dating (10Be) of quartzite cobbles along the vertical fault scarp yields young exposure ages that can be bracketed between 0 to 6 ka, depending on the inheritance model that is applied. Our preferred scenario, which takes in account our geomorphic observations, implies at least two distinct rupture events, each associated with 3 and 2 m of vertical offset. These two events plausibly occurred during the last thousand years. Nevertheless, an interpretation invoking more tectonic events along the fault cannot be ruled out. This work affirms crustal deformation along active faults in the Andean forearc of southern Peru during the last thousand years.
Plate tectonics on Venus

NASA Technical Reports Server (NTRS)

Anderson, D. L.

1981-01-01

The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.
Relationships between sinkholes areal distribution and main tectonic alignments in Abruzzo (Central Italy)

NASA Astrophysics Data System (ADS)

Ferrini, G.; Moretti, A.; De Rose, C.; Stagnini, E.,; Serafini, M.

2012-04-01

Intermountain basins, developed at the back side of the Apennines overturning front, are the most evident morphological expressions of extensional tectonics in Central Italy and can be recognized in many different sections of the chain. L'Aquila basin and the adjoining Subequana valley are part of a single NW-SE elongated depression (about 60 km long) which began to develop about in the early Quaternary in response to the identification of various regional extensional tectonic alignments and the consequent starting of the basin subsidence. This impressive morphological element is characterized by the presence of several large funnel-shaped features (locally named Fosse = trench) which affect mainly the Meso-Cenozoic carbonatic bedrock but also the Neogenic clastic sedimentary filling of the valley. Some of these last elements are often occupied by ponds or significant artesian water resurgences like the Sinizzo Lake where, during L'Aquila earthquake of April 6th 2009, the shores collapsed and strong microseismic activity, deep rumbles and flow rate changes were reported for the following months. The Fosse mapped in the L'Aquila basin have widths in the order of hundreds of meters, a considerable difference of elevation respect the rims and present a general morphology very close to that of the classic dissolution karst sinkholes. Their evolution/localization is strictly related to the active fault systems which controls also the main tracts of the relief; the low volume of residual sedimentary deposits within the depression, not comparable with the total volume of rock removed, indicates that surface karst dissolution phenomena are absent or secondary. The elevations of the floor of many Fosse are higher respect the actual flood plain depending on their age; in fact relict circular forms, recognizable at upper altitude on the relief slope, confirm that the phenomenon has been active for a considerable period of time. About the genesis of this features, even if at
Active tectonics of the onshore Hengchun Fault using UAS DSM combined with ALOS PS-InSAR time series (Southern Taiwan)

NASA Astrophysics Data System (ADS)

Deffontaines, Benoit; Chang, Kuo-Jen; Champenois, Johann; Lin, Kuan-Chuan; Lee, Chyi-Tyi; Chen, Rou-Fei; Hu, Jyr-Ching; Magalhaes, Samuel

2018-03-01

Characterizing active faults and quantifying their activity are major concerns in Taiwan, especially following the major Chichi earthquake on 21 September 1999. Among the targets that still remain poorly understood in terms of active tectonics are the Hengchun and Kenting faults (Southern Taiwan). From a geodynamic point of view, the faults affect the outcropping top of the Manila accretionary prism of the Manila subduction zone that runs from Luzon (northern Philippines) to Taiwan. In order to better locate and quantify the location and quantify the activity of the Hengchun Fault, we start from existing geological maps, which we update thanks to the use of two products derived from unmanned aircraft system acquisitions: (1) a very high precision (< 50 cm) and resolution (< 10 cm) digital surface model (DSM) and (2) a georeferenced aerial photograph mosaic of the studied area. Moreover, the superimposition of the resulting structural sketch map with new Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) results obtained from PALSAR ALOS images, validated by Global Positioning System (GPS) and leveling data, allows the characterization and quantification of the surface displacements during the monitoring period (2007-2011). We confirm herein the geometry, characterization and quantification of the active Hengchun Fault deformation, which acts as an active left-lateral transpressive fault. As the Hengchun ridge was the location of one of the last major earthquakes in Taiwan (26 December 2006, depth: 44 km, ML = 7.0), Hengchun Peninsula active tectonics must be better constrained in order if possible to prevent major destructions in the near future.
New Insights on Mt. Etna's Crust and Relationship with the Regional Tectonic Framework from Joint Active and Passive P-Wave Seismic Tomography

NASA Astrophysics Data System (ADS)

Díaz-Moreno, A.; Barberi, G.; Cocina, O.; Koulakov, I.; Scarfì, L.; Zuccarello, L.; Prudencio, J.; García-Yeguas, A.; Álvarez, I.; García, L.; Ibáñez, J. M.

2018-01-01

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g., those from Mt. Etna and the Aeolian Islands archipelago) testifies to the complexity of the tectonic and geodynamic setting. Despite the large number of studies that have focused on this area, the relationships among volcanism, tectonics, magma ascent, and geodynamic processes remain poorly understood. We present a tomographic inversion of P-wave velocity using active and passive sources. Seismic signals were recorded using both temporary on-land and ocean bottom seismometers and data from a permanent local seismic network consisting of 267 seismic stations. Active seismic signals were generated using air gun shots mounted on the Spanish Oceanographic Vessel `Sarmiento de Gamboa'. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month period. In total, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different velocity models. Our results include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan-southern Calabria region and both the Mt. Etna and Aeolian volcanic environments. The tomographic images provide a detailed and complete regional seismotectonic framework and highlight a spatially heterogeneous tectonic regime, which is consistent with and extends the findings of previous models. One of our most significant results was a tomographic map extending to 14 km depth showing a discontinuity striking roughly NW-SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, corresponding to the Aeolian-Tindari-Letojanni fault system, a regional deformation belt. Moreover, for the first time, we observed a high-velocity anomaly located in the south-eastern sector of the Mt. Etna region, offshore of the Timpe area, which is compatible with the plumbing system of an ancient shield volcano located offshore of Mt. Etna.
New Insights into Tectonics of the Saint Elias, Alaska, Region Based on Local Seismicity and Tomography

NASA Astrophysics Data System (ADS)

Ruppert, N. A.; Zabelina, I.; Freymueller, J. T.

2013-12-01

Saint Elias Mountains in southern Alaska are manifestation of ongoing tectonic processes that include collision of the Yakutat block with and subduction of the Yakutat block and Pacific plate under the North American plate. Interaction of these tectonic blocks and plates is complex and not well understood. In 2005 and 2006 a network of 22 broadband seismic sites was installed in the region as part of the SainT Elias TEctonics and Erosion Project (STEEP), a five-year multi-disciplinary study that addressed evolution of the highest coastal mountain range on Earth. High quality seismic data provides unique insights into earthquake occurrence and velocity structure of the region. Local earthquake data recorded between 2005 and 2010 became a foundation for detailed study of seismotectonic features and crustal velocities. The highest concentration of seismicity follows the Chugach-St.Elias fault, a major on land tectonic structure in the region. This fault is also delineated in tomographic images as a distinct contrast between lower velocities to the south and higher velocities to the north. The low-velocity region corresponds to the rapidly-uplifted and exhumed sediments on the south side of the range. Earthquake source parameters indicate high degree of compression and undertrusting processes along the coastal area, consistent with multiple thrust structures mapped from geological studies in the region. Tomographic inversion reveals velocity anomalies that correlate with sedimentary basins, volcanic features and subducting Yakutat block. We will present precise earthquake locations and source parameters recorded with the STEEP and regional seismic network along with the results of P- and S-wave tomographic inversion.
Active tectonic deformation along rejuvenated faults in tropical Borneo: Inferences obtained from tectono-geomorphic evaluation

NASA Astrophysics Data System (ADS)

Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Kumar, Shashi Gaurav; Authemayou, Christine

2016-08-01

The island of Borneo is enveloped by tropical rainforests and hostile terrain characterized by high denudation rates. Owing to such conditions, studies pertaining to neotectonics and consequent geomorphic expressions with regard to surface processes and landscape evolution are inadequately constrained. Here we demonstrate the first systematic tectono-geomorphic evaluation of north Borneo through quantitative and qualitative morphotectonic analysis at sub-catchment scale, for two large drainage basins located in Sarawak: the Rajang and Baram basins. The extraction of morphometric parameters utilizing digital elevation models arranged within a GIS environment focuses on hypsometric curve analysis, distribution of hypsometric integrals through spatial autocorrelation statistics, relative uplift values, the asymmetry factor and the normalized channel steepness index. Hypsometric analysis suggests a young topography adjusting to changes in tectonic boundary conditions. Autocorrelation statistics show clusters of high values of hypsometric integrals as prominent hotspots that are associated with less eroded, young topography situated in the fold and thrust belts of the Interior Highlands of Borneo. High channel steepness and gradients (> 200 m0.9) are observed in zones corresponding to the hotspots. Relative uplift values reveal the presence of tectonically uplifted blocks together with relatively subsided or lesser uplifted zones along known faults. Sub-catchments of both basins display asymmetry indicating tectonic tilting. Stream longitudinal profiles demonstrate the presence of anomalies in the form of knickzones without apparent lithological controls along their channel reaches. Surfaces represented by cold spots of low HI values and low channel gradients observed in the high elevation headwaters of both basins are linked to isolated erosional planation surfaces that could be remnants of piracy processes. The implication of our results is that Borneo experiences
Structural and tectonic setting of the Charleston, South Carolina, region: Evidence from the Tertiary stratigraphic record

USGS Publications Warehouse

Weems, R.E.; Lewis, W.C.

2002-01-01

Eleven upper Eocene through Pliocene stratigraphic units occur in the subsurface of the region surrounding Charleston, South Carolina. These units contain a wealth of information concerning the long-term tectonic and structural setting of that area. These stratigraphic units have a mosaic pattern of distribution, rather than a simple layered pattern, because deposition, erosion, and tectonic warping have interacted in a complex manner through time. By generating separate structure-contour maps for the base of each stratigraphic unit, an estimate of the original basal surface of each unit can be reconstructed over wide areas. Changes in sea level over geologic time generate patterns of deposition and erosion that are geographically unique for the time of each transgression. Such patterns fail to persist when compared sequentially over time. In some areas, however, there has been persistent, repetitive net downward of upward movement over the past 34 m.y. These repetitive patterns of persistent motion are most readily attributable to tectonism. The spatial pattern of these high and low areas is complex, but it appears to correlate well with known tectonic features of the region. This correlation suggests that the tectonic setting of the Charleston region is controlled by scissors-like compression on a crustal block located between the north-trending Adams Run fault and the northwest-trending Charleston fault. Tectonism is localized in the Charleston region because it lies within a discrete hinge zone that accommodates structural movement between the Cape Fear arch and the Southeast Georgia embayment.
Spiral tectonics

NASA Astrophysics Data System (ADS)

Hassan Asadiyan, Mohammad

2014-05-01

Spiral Tectonics (ST) is a new window to global tectonics introduced as alternative model for Plate Tectonics (PT). ST based upon Dahw(rolling) and Tahw(spreading) dynamics. Analogues to electric and magnetic components in the electromagnetic theory we could consider Dahw and Tahw as components of geodynamics, when one component increases the other decreases and vice versa. They are changed to each other during geological history. D-component represents continental crust and T-component represents oceanic crust. D and T are two arm of spiral-cell. T-arm 180 degree lags behind D-arm so named Retard-arm with respect to D or Forward-arm. It seems primary cell injected several billions years ago from Earth's center therefore the Earth's core was built up first then mantel and finally the crust was build up. Crust building initiate from Arabia (Mecca). As the universe extended gravitation wave swirled the earth fractaly along cycloid path from big to small scale. In global scale (order-0) ST collect continents in one side and abandoned Pacific Ocean in the other side. Recent researches also show two mantels upwelling in opposite side of the Earth: one under Africa (tectonic pose) and the other under Pacific Ocean (tectonic tail). In higher order (order-1) ST build up Africa in one side and S.America in the other side therefore left Atlantic Ocean meandered in between. In order-n e.g. Khoor Musa and Bandar-Deylam bay are seen meandered easterly in the Iranian part but Khoor Abdullah and Kuwait bay meandered westerly in the Arabian part, they are distributed symmetrically with respect to axis of Persian Gulf(PG), these two are fractal components of easterly Caspian-wing and westerly Black Sea-wing which split up from Anatoly. Caspian Sea and Black Sea make two legs of Y-like structure, this shape completely fitted with GPS-velocity map which start from PG and split up in the Catastrophic Point(Anatoly). We could consider PG as remnants of Ancient Ocean which spent up
Tectonic map of Liberia based on geophysical and geological surveys

USGS Publications Warehouse

Behrendt, John Charles; Wotorson, Cletus S.

1972-01-01

Interpretation of the results of aeromagnetic, total-gamma radioactivity, and gravity surveys combined with geologic data for Western Liberia from White and Leo (1969) and other geologic information allows the construction of a tectonic map of Liberia. The map approximately delineates the boundaries between the Liberian (ca. 2700 m.y.) province in the northwestern two-thirds of the country, the Eburnean (ca. 2000 m.y.) province in the south-eastern one-third, and the Pan-African (ca. 550 m.y.) province in the coastal area of the northwestern two-thirds of the country. Rock follation and tectonic structural features trend northeastward in the Liberian province, east-northeastward to north-northeastward in the Eburnean province, and northwestward in the Pan-African age province. Linear residual magnetic anomailes 20-80 km wide and 200-600 gammas in amplitude and following the northeast structural trend typical of the Liberian age province cross the entire country and extend into Sierra Leone and Ivory Coast.
Primary centers and secondary concentrations of tectonic activity through time in the western hemisphere of Mars

USGS Publications Warehouse

Anderson, R.C.; Dohm, J.M.; Golombek, M.P.; Haldemann, A.F.C.; Franklin, B.J.; Tanaka, K.L.; Lias, J.; Peer, B.

2001-01-01

Five main stages of radial and concentric structures formed around Tharsis from the Noachian through the Amazonian as determined by geologic mapping of 24,452 structures within the stratigraphic framework of Mars and by testing their radial and concentric orientations. Tectonic activity peaked in the Noachian (stage 1) around the largest center, Claritas, an elongate center extending more than 20?? in latitude and defined by about half of the total grabens which are concentrated in the Syria Planum, Thaumasia, and Tempe Terra regions. During the Late Noachian and Early Hesperian (stage 2), extensional structures formed along the length of present-day Valles Marineris and in Thaumasia (with a secondary concentration near Warrego Vallis) radial to a region just to the south of the central margin of Valles Marineris. Early Hesperian (stage 3) radial grabens in Pavonis, Syria, Ulysses, and Tempe Terra and somewhat concentric wrinkle ridges in Lunae and Solis Plana and in Thaumasia, Sirenum, Memnonia, and Amazonis are centered northwest of Syria with secondary centers at Thaumasia, Tempe Terra, Ulysses Fossae, and western Valles Marineris. Late Hesperian/Early Amazonian (stage 4) structures around Alba Patera, the northeast trending alignment of Tharsis Montes, and Olympus Mons appears centered on Alba Patera. Stage 5 structures (Middle-Late Amazonian) represent the last pulse of Tharsis-related activity and are found around the large shield volcanoes and are centered near Pavonis Mons. Tectonic activity around Tharsis began in the Noachian and generally decreased through geologic time to the Amazonian. Statistically significant radial distributions of structures formed during each stage, centered at different locations within the higher elevations of Tharsis. Secondary centers of radial structures during many of the stages appear related to previously identified local magmatic centers that formed at different times and locations throughout Tharsis. Copyright 2001 by
Spreading continents kick-started plate tectonics.

PubMed

Rey, Patrice F; Coltice, Nicolas; Flament, Nicolas

2014-09-18

Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics, which characterizes the present-day geodynamics of the Earth. Because the Earth's interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present, and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models. Here we show that because the oceanic crust was thick and buoyant, early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons. Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity. The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining.
Global organization of tectonic deformation on Venus

NASA Astrophysics Data System (ADS)

Bilotti, Frank; Connors, Chris; Suppe, John

1993-03-01

The geographic organization of surface deformation on Venus as on Earth is a key to understanding the global tectonic system. To date we have mapped the distribution of three unambiguous tectonic land forms on Venus: (1) linear foldbelts analogous to those at plate margins of the Earth; (2) linear rift zones, analogous to continental rifts on the Earth; and (3) distributed plains deformation in the form of wrinkle ridges and extensional faults and fractures. The linear foldbelts are the dominant structural style in the Northern Hemisphere; ninety percent of the planet's foldbelts lie above the equator. In contrast, compressive deformation in the Southern Hemisphere is dominated by two large, sweeping patterns of wrinkle ridges. The two hemispheres are divided by an equatorial region that is largely covered by rift zones and several large tessera blocks. A tectonic model of generally poleward convergence of the Northern Hemisphere explains the distribution of foldbelts and rift zones. In our model, a northern hemispherical plate (or system of plates) moves poleward and deforms along discrete, predominately longitudinal bands. We recognize four types of foldbelts based on their relationships to other large-scale tectonic features on Venus. There are foldbelts that lie within the low plains, foldbelts associated with coronae, novae and chasmata, foldbelts that lie at the margins of poly-deformed tessera plateaus, and the folded mountain belts around Lakshmi Planum. We see a geometric increase in the area of fold belts when normalized to percent area at a given latitude. This increase is consistent with our model of poleward convergence. Also, the orientations of most foldbelts are either approximately north-south or parallel to lines of latitude in the northern hemisphere. This observation is also consistent with the model in that the longitudinal bands are the result of the decreasing area of the sphere as the plate moves poleward and the latitudinal belts are the
Global organization of tectonic deformation on Venus

NASA Technical Reports Server (NTRS)

Bilotti, Frank; Connors, Chris; Suppe, John

1993-01-01

The geographic organization of surface deformation on Venus as on Earth is a key to understanding the global tectonic system. To date we have mapped the distribution of three unambiguous tectonic land forms on Venus: (1) linear foldbelts analogous to those at plate margins of the Earth; (2) linear rift zones, analogous to continental rifts on the Earth; and (3) distributed plains deformation in the form of wrinkle ridges and extensional faults and fractures. The linear foldbelts are the dominant structural style in the Northern Hemisphere; ninety percent of the planet's foldbelts lie above the equator. In contrast, compressive deformation in the Southern Hemisphere is dominated by two large, sweeping patterns of wrinkle ridges. The two hemispheres are divided by an equatorial region that is largely covered by rift zones and several large tessera blocks. A tectonic model of generally poleward convergence of the Northern Hemisphere explains the distribution of foldbelts and rift zones. In our model, a northern hemispherical plate (or system of plates) moves poleward and deforms along discrete, predominately longitudinal bands. We recognize four types of foldbelts based on their relationships to other large-scale tectonic features on Venus. There are foldbelts that lie within the low plains, foldbelts associated with coronae, novae and chasmata, foldbelts that lie at the margins of poly-deformed tessera plateaus, and the folded mountain belts around Lakshmi Planum. We see a geometric increase in the area of fold belts when normalized to percent area at a given latitude. This increase is consistent with our model of poleward convergence. Also, the orientations of most foldbelts are either approximately north-south or parallel to lines of latitude in the northern hemisphere. This observation is also consistent with the model in that the longitudinal bands are the result of the decreasing area of the sphere as the plate moves poleward and the latitudinal belts are the
Creating global comparative analyses of tectonic rifts, monogenetic volcanism and inverted relief

NASA Astrophysics Data System (ADS)

van Wyk de Vries, Benjamin

2016-04-01

I have been all around the world, and to other planets and have travelled from the present to the Archaean and back to seek out the most significant tectonic rifts, monogenetic volcanoes and examples of inverted relief. I have done this to provide a broad foundation of the comparative analysis for the Chaîne des Puys - Limagne fault nomination to UNESCO world Heritage. This would have been an impossible task, if not for the cooperation of the scientific community and for Google Earth, Google Maps and academic search engines. In preparing global comparisons of geological features, these quite recently developed tools provide a powerful way to find and describe geological features. The ability to do scientific crowd sourcing, rapidly discussing with colleagues about features, allows large numbers of areas to be checked and the open GIS tools (such as Google Earth) allow a standardised description. Search engines also allow the literature on areas to be checked and compared. I will present a comparative study of rifts of the world, monogenetic volcanic field and inverted relief, integrated to analyse the full geological system represented by the Chaîne des Puys - Limagne fault. The analysis confirms that the site is an exceptional example of the first steps of continental drift in a mountain rift setting, and that this is necessarily seen through the combined landscape of tectonic, volcanic and geomorphic features. The analysis goes further to deepen the understanding of geological systems and stresses the need for more study on geological heritage using such a global and broad systems approach.
Channel flow and localized fault bounded slice tectonics (LFBST): Insights from petrological, structural, geochronological and geospeedometric studies in the Sikkim Himalaya, NE India

NASA Astrophysics Data System (ADS)

Chakraborty, Sumit; Mukhopadhyay, Dilip K.; Chowdhury, Priyadarshi; Rubatto, Daniela; Anczkiewicz, Robert; Trepmann, Claudia; Gaidies, Fred; Sorcar, Nilanjana; Dasgupta, Somnath

2017-06-01

One of the enduring debates in the study of the Himalayan orogen (and continental collision zones in general) is whether the salient observed features are explained (a) by localized deformation along discrete, narrow fault zones/ductile shear zones separating individual blocks or slices (e.g. critical taper or wedge tectonic models), or (b) by distributed deformation dominated by wide zones of visco-plastic flow in the solid or a partially molten state (e.g. channel flow models). A balanced cross-section from Sikkim in the eastern Himalaya that is based on structural data and is drawn to satisfy petrological and geophysical constraints as well, is used in combination with information from petrology, geochronology, geospeedometry and microstructural data to address this question. We discuss that any tectonic model needs to be thermally, rheologically, geometrically and temporally viable in order to qualify as a suitable description of a system; models such as channel flow and critical taper are considered in this context. It is shown that channel flow models may operate with or without an erosional porthole (channel with tunnel and funnel mode vs. channels with only the tunnel mode) and that the predicted features differ significantly between the two. Subsequently, we consider a large body of data from Sikkim to show that a channel flow type model (in the tunneling without funneling mode), such as the ones of Faccenda et al. (2008), describes features formed at high temperatures very well, while features formed at lower temperatures are more consistent with the operation of localized, fault-bounded, slice tectonics, (LFBST, be it in the form of critical taper, wedge tectonics, or something else). Thus, the two modes are not competing, but collaborating, processes and both affect a given rock unit at different points of time during burial, metamorphism and exhumation. A transitional stage separates the two end-member styles of tectonic evolution. The proposed models
Persistent Scatterer Interferometry analysis of ground deformation in the Po Plain (Piacenza-Reggio Emilia sector, Northern Italy): seismo-tectonic implications

NASA Astrophysics Data System (ADS)

Antonielli, Benedetta; Monserrat, Oriol; Bonini, Marco; Cenni, Nicola; Devanthéry, Núria; Righini, Gaia; Sani, Federico

2016-08-01

This work aims to explore the ongoing tectonic activity of structures in the outermost sector of the Northern Apennines, which represents the active leading edge of the thrust belt and is dominated by compressive deformation. We have applied the Persistent Scatterer Interferometry (PSI) technique to obtain new insights into the present-day deformation pattern of the frontal area of the Northern Apennine. PSI has proved to be effective in detecting surface deformation of wide regions involved in low tectonic movements. We used 34 Envisat images in descending geometry over the period of time between 2004 and 2010, performing about 300 interferometric pairs. The analysis of the velocity maps and of the PSI time-series has allowed to observe ground deformation over the sector of the Po Plain between Piacenza and Reggio Emilia. The time-series of permanent GPS stations located in the study area, validated the results of the PSI technique, showing a good correlation with the PS time-series. The PS analysis reveals the occurrence of a well-known subsidence area on the rear of the Ferrara arc, mostly connected to the exploitation of water resources. In some instances, the PS velocity pattern reveals ground uplift (with mean velocities ranging from 1 to 2.8 mm yr-1) above active thrust-related anticlines of the Emilia and Ferrara folds, and part of the Pede-Apennine margin. We hypothesize a correlation between the observed uplift deformation pattern and the growth of the thrust-related anticlines. As the uplift pattern corresponds to known geological features, it can be used to constrain the seismo-tectonic setting, and a working hypothesis may involve that the active Emilia and Ferrara thrust folds would be characterized by interseismic periods possibly dominated by aseismic creep.

Activity Analyses for Solar-type Stars Observed with Kepler. II. Magnetic Feature versus Flare Activity

NASA Astrophysics Data System (ADS)

He, Han; Wang, Huaning; Zhang, Mei; Mehrabi, Ahmad; Yan, Yan; Yun, Duo

2018-05-01

The light curves of solar-type stars present both periodic fluctuation and flare spikes. The gradual periodic fluctuation is interpreted as the rotational modulation of magnetic features on the stellar surface and is used to deduce magnetic feature activity properties. The flare spikes in light curves are used to derive flare activity properties. In this paper, we analyze the light curve data of three solar-type stars (KIC 6034120, KIC 3118883, and KIC 10528093) observed with Kepler space telescope and investigate the relationship between their magnetic feature activities and flare activities. The analysis shows that: (1) both the magnetic feature activity and the flare activity exhibit long-term variations as the Sun does; (2) unlike the Sun, the long-term variations of magnetic feature activity and flare activity are not in phase with each other; (3) the analysis of star KIC 6034120 suggests that the long-term variations of magnetic feature activity and flare activity have a similar cycle length. Our analysis and results indicate that the magnetic features that dominate rotational modulation and the flares possibly have different source regions, although they may be influenced by the magnetic field generated through a same dynamo process.
MANTLE CONVECTION, PLATE TECTONICS, AND VOLCANISM ON HOT EXO-EARTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Summeren, Joost; Conrad, Clinton P.; Gaidos, Eric, E-mail: summeren@hawaii.edu

Recently discovered exoplanets on close-in orbits should have surface temperatures of hundreds to thousands of Kelvin. They are likely tidally locked and synchronously rotating around their parent stars and, if an atmosphere is absent, have surface temperature contrasts of many hundreds to thousands of Kelvin between permanent day and night sides. We investigated the effect of elevated surface temperature and strong surface temperature contrasts for Earth-mass planets on the (1) pattern of mantle convection, (2) tectonic regime, and (3) rate and distribution of partial melting, using numerical simulations of mantle convection with a composite viscous/pseudo-plastic rheology. Our simulations indicate thatmore » if a close-in rocky exoplanet lacks an atmosphere to redistribute heat, a {approx}>400 K surface temperature contrast can maintain an asymmetric degree 1 pattern of mantle convection in which the surface of the planet moves preferentially toward subduction zones on the cold night side. The planetary surface features a hemispheric dichotomy, with plate-like tectonics on the night side and a continuously evolving mobile lid on the day side with diffuse surface deformation and vigorous volcanism. If volcanic outgassing establishes an atmosphere and redistributes heat, plate tectonics is globally replaced by diffuse surface deformation and volcanism accelerates and becomes distributed more uniformly across the planetary surface.« less
Seafloor morphology related to recent tectonics in the Alboran Sea Basin

NASA Astrophysics Data System (ADS)

Vázquez, Juan-Tomás; Estrada, Ferran; Vegas, Ramon; Ercilla, Gemma; Medialdea, Teresa; d'Acremont, Elia; Alonso, Belen; Fernández-Salas, Luis-Miguel; Gómez-Ballesteros, María; Somoza, Luis; Bárcenas, Patricia; Palomino, Desirée; Gorini, Christian

2014-05-01

A detailed geomorphological study of the northern part of the Alboran Sea Basin has been realized based on the combined analysis of multibeam swath bathymetric data and medium to very high resolution seismic profiles (singled Sparker, Airgun, TOPAS and Atlas PARASOUND P35). This has enabled us to define several tectonic-related seafloor features and their role in the recent tectonics. The observed morpho-tectonic features correspond to: i) lineal scarps with a wide range of dimensions and following several trends ,WNW-ESE, NE-SW, NNE-SSW and N-S; ii) NE-SW to NNE-SSW-oriented compressive ridges; iii) ENE-WSW to NE-SW-striking antiforms; iv) NNE-SSW-oriented lineal depressions; v) rhomb-shaped depressions; vi) lineal valleys, canyons and gullies with WNW-ESE, and N-S orientations; and vii) N-S directed dissected valleys, canyons and gullies. Three families of faults and related folds, with NE-SW, WNW-ESE and NNE-SSW to N-S have been interpreted within this geomorphological scheme. The NE-SW family corresponds to: a) major scarps in both flanks of the Alboran Ridge and b) the offshore prolongation of La Serrata Fault, and both have been considered as a set of sinistral strike-slip faults. To this family, some compressive ridges, antiforms and occasionally reverse faults have been correlated. The WNW-ESE family corresponds to a set of faulted valleys (occasionally with rhomb-shaped depressions), fault scarps and linear inflection points occurring in the northern Alboran margin and the Yusuf-Habibas corridor. This family has been interpreted as transtensive dextral strike-slip faults. The NNE-SSW to N-S family corresponds to a penetrative system of linear fault scarps and tectonic depressions that cross-cut the Alboran Ridge and the Djibouti-Motril marginal plateau. This family can be considered as more recent since it offsets the other two families and shows a minor importance with regard to the main reliefs. This communication is a contribution to the Spanish R + D
Active tectonics around the Yakutat indentor: New geomorphological constraints on the eastern Denali, Totschunda and Duke River Faults

NASA Astrophysics Data System (ADS)

Marechal, Anaïs; Ritz, Jean-François; Ferry, Matthieu; Mazzotti, Stephane; Blard, Pierre-Henri; Braucher, Régis; Saint-Carlier, Dimitri

2018-01-01

The Yakutat collision in SE Alaska - SW Yukon is an outstanding example of indentor tectonics. The impinging Yakutat block strongly controls the pattern of deformation inland. However, the relationship between this collision system and inherited tectonic structures such as the Denali, Totschunda, and Duke River Faults remains debated. A detailed geomorphological analysis, based on high-resolution imagery, digital elevation models, field observations, and cosmogenic nuclide dating, allow us to estimate new slip rates along these active structures. Our results show a vertical motion of 0.9 ± 0.3 mm/yr along the whole eastern Denali Fault, while the dextral component of the fault tapers to less than 1 mm/yr ∼80 km south of the Denali-Totschunda junction. In contrast, the Totschunda Fault accommodates 14.6 ± 2.7 mm/yr of right-lateral strike-slip along its central section ∼100 km south of the junction. Further south, preliminary observations suggest a slip rate comprised between 3.5 and 6.5 mm/yr along the westernmost part of the Duke River thrust fault. Our results highlight the complex partitioning of deformation inland of the Yakutat collision, where the role and slip rate of the main faults vary significantly over distances of ∼100 km or less. We propose a schematic model of present-day tectonics that suggests ongoing partitioning and reorganization of deformation between major inherited structures, relay zones, and regions of distributed deformation, in response to the radial stress and strain pattern around the Yakutat collision eastern syntaxis.
Plate tectonics, damage and inheritance.

PubMed

Bercovici, David; Ricard, Yanick

2014-04-24

The initiation of plate tectonics on Earth is a critical event in our planet's history. The time lag between the first proto-subduction (about 4 billion years ago) and global tectonics (approximately 3 billion years ago) suggests that plates and plate boundaries became widespread over a period of 1 billion years. The reason for this time lag is unknown but fundamental to understanding the origin of plate tectonics. Here we suggest that when sufficient lithospheric damage (which promotes shear localization and long-lived weak zones) combines with transient mantle flow and migrating proto-subduction, it leads to the accumulation of weak plate boundaries and eventually to fully formed tectonic plates driven by subduction alone. We simulate this process using a grain evolution and damage mechanism with a composite rheology (which is compatible with field and laboratory observations of polycrystalline rocks), coupled to an idealized model of pressure-driven lithospheric flow in which a low-pressure zone is equivalent to the suction of convective downwellings. In the simplest case, for Earth-like conditions, a few successive rotations of the driving pressure field yield relic damaged weak zones that are inherited by the lithospheric flow to form a nearly perfect plate, with passive spreading and strike-slip margins that persist and localize further, even though flow is driven only by subduction. But for hotter surface conditions, such as those on Venus, accumulation and inheritance of damage is negligible; hence only subduction zones survive and plate tectonics does not spread, which corresponds to observations. After plates have developed, continued changes in driving forces, combined with inherited damage and weak zones, promote increased tectonic complexity, such as oblique subduction, strike-slip boundaries that are subparallel to plate motion, and spalling of minor plates.
A geographic comparison of selected large-scale planetary surface features

NASA Technical Reports Server (NTRS)

Meszaros, S. P.

1984-01-01

Photographic and cartographic comparisons of geographic features on Mercury, the Moon, Earth, Mars, Ganymede, Callisto, Mimas, and Tethys are presented. Planetary structures caused by impacts, volcanism, tectonics, and other natural forces are included. Each feature is discussed individually and then those of similar origin are compared at the same scale.
Burke new Tectonics editor

NASA Astrophysics Data System (ADS)

Kevin C. Burke, National Academy of Sciences/ National Research Council (NAS/NRC), assumed responsibilities as Editor in Chief of the American Geophysical Union (AGU) journal Tectonics at the beginning of 1990, taking over from Raymond A. Price, Queens University, Kingston, Ontario. Asger Berthelsen, University of Copenhagen, Denmark, continues as the European Editor, and Paul F. Hoffman, Geological Society of Canada, assumes the task of North American Editor. Tectonics is a joint publication of AGU and the European Geophysical Society.
Tectonic and metallogenic model for northeast Asia

USGS Publications Warehouse

Parfenov, Leonid M.; Nokleberg, Warren J.; Berzin, Nikolai A.; Badarch, Gombosuren; Dril, Sergy I.; Gerel, Ochir; Goryachev, Nikolai A.; Khanchuk, Alexander I.; Kuz'min, Mikhail I.; Prokopiev, Andrei V.; Ratkin, Vladimir V.; Rodionov, Sergey M.; Scotese, Christopher R.; Shpikerman, Vladimir I.; Timofeev, Vladimir F.; Tomurtogoo, Onongin; Yan, Hongquan; Nokleberg, Warren J.

2011-01-01

This document describes the digital files in this report that contains a tectonic and metallogenic model for Northeast Asia. The report also contains background materials. This tectonic and metallogenic model and other materials on this report are derived from (1) an extensive USGS Professional Paper, 1765, on the metallogenesis and tectonics of Northeast Asia that is available on the Internet at http://pubs.usgs.gov/pp/1765/; and (2) the Russian Far East parts of an extensive USGS Professional Paper, 1697, on the metallogenesis and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera that is available on the Internet at http://pubs.usgs.gov/pp/pp1697/. The major purpose of the tectonic and metallogenic model is to provide, in movie format, a colorful summary of the complex geology, tectonics, and metallogenesis of the region. To accomplish this goal four steps were taken: (1) 13 time-stage diagrams, from the late Neoproterozoic (850 Ma) through the present (0 Ma), were adapted, generalized, and transformed into color static time-stage diagrams; (2) the 13 time-stage diagrams were placed in a computer morphing program to produce the model; (3) the model was examined and each diagram was successively adapted to preceding and subsequent diagrams to match the size and surface expression of major geologic units; and (4) the final version of the model was produced in successive iterations of steps 2 and 3. The tectonic and metallogenic model and associated materials in this report are derived from a project on the major mineral deposits, metallogenesis, and tectonics of the Northeast Asia and from a preceding project on the metallogenesis and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera. Both projects provide critical information on bedrock geology and geophysics, tectonics, major metalliferous mineral resources, metallogenic patterns, and crustal origin and evolution of mineralizing systems for this region. The major
Overview of the Education and Public Outreach (EPO) program of the Caltech Tectonics Observatory

NASA Astrophysics Data System (ADS)

Kovalenko, L.; Jain, K.; Maloney, J.

2009-12-01

The Caltech Tectonics Observatory (TO) is an interdisciplinary center, focused on geological processes occurring at the boundaries of Earth's tectonic plates (http://www.tectonics.caltech.edu). Over the past year, the TO has made a major effort to develop an Education and Public Outreach (EPO) program. Our goals are to (1) stimulate the interest of students and the general public in Earth Sciences, particularly in the study of tectonic processes, (2) inform and educate the general public about science in the context of TO discoveries and advancements, and (3) provide opportunities for graduate students, postdocs, and faculty to do outreach in the local K-12 schools. We have hosted local high school students and teachers to provide them with research experience (as part of Caltech’s “Summer Research Connection”); participated in teacher training workshops (organized by the local school district); hosted tours for local elementary school students; and brought hands-on activities into local elementary and middle school classrooms, science clubs, and science nights. We have also led local school students and teachers on geology field trips through nearby parks. In addition, we have developed education modules for undergraduate classes (as part of MARGINS program), and have written educational web articles on TO research (http://www.tectonics.caltech.edu/outreach). The presentation will give an overview of these activities and their impact on our educational program.
Parallel Extension Tectonics (PET): Early Cretaceous tectonic extension of the Eastern Eurasian continent

NASA Astrophysics Data System (ADS)

Liu, Junlai; Ji, Mo; Ni, Jinlong; Guan, Huimei; Shen, Liang

2017-04-01

The present study reports progress of our recent studies on the extensional structures in eastern North China craton and contiguous areas. We focus on characterizing and timing the formation/exhumation of the extensional structures, the Liaonan metamorphic core complex (mcc) and the Dayingzi basin from the Liaodong peninsula, the Queshan mcc, the Wulian mcc and the Zhucheng basin from the Jiaodong peninsula, and the Dashan magmatic dome within the Sulu orogenic belt. Magmatic rocks (either volcanic or plutonic) are ubiquitous in association with the tectonic extension (both syn- and post-kinematic). Evidence for crustal-mantle magma mixing are popular in many syn-kinematic intrusions. Geochemical analysis reveals that basaltic, andesitic to rhyolitic magmas were generated during the tectonic extension. Sr-Nd isotopes of the syn-kinematic magmatic rocks suggest that they were dominantly originated from ancient or juvenile crust partly with mantle signatures. Post-kinematic mafic intrusions with ages from ca. 121 Ma to Cenozoic, however, are of characteristic oceanic island basalts (OIB)-like trace element distribution patterns and relatively depleted radiogenic Sr-Nd isotope compositions. Integrated studies on the extensional structures, geochemical signatures of syn-kinematic magmatic rocks (mostly of granitic) and the tectono-magmatic relationships suggest that extension of the crust and the mantle lithosphere triggered the magmatisms from both the crust and the mantle. The Early Cretaceous tectono-magmatic evolution of the eastern Eurasian continent is governed by the PET in which the tectonic processes is subdivided into two stages, i.e. an early stage of tectonic extension, and a late stage of collapse of the extended lithosphere and transformation of lithospheric mantle. During the early stage, tectonic extension of the lithosphere led to detachment faulting in both the crust and mantle, resulted in the loss of some of the subcontinental roots, gave rise to
Tectonic geomorphology of the New Madrid seismic zone based on imaging of digital topographic data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayer, L.

1993-03-01

Topographic analysis using digital elevation data of the New Madrid region focuses on topographic features that occur at several spatial scales and can be used to delineate distinct anomalies. In this region, topographic anomalies occur as domal or elongate uplifts and bowl-shaped depressions approximately 1--10 km in size, topographic lineaments, and differences in topographic blocking across 50 km long boundaries. In order to fully explain these topographic anomalies, tectonic processes may be required. Imaging is based on digital topographic data from USGS 30 arc-second, 3 arc-second, and 30 m resolutions. Imaging of these data uses standard imaging processing techniques tomore » examine topography within the contexts of geomorphological hypothesis testing. A good example is the use of thresholding to highlight areas of unusually high elevation given the hypothesis of fluvial landscape architecture. Thresholding delineates topographic features such as the Tiptonville dome which is strongly believed to be tectonic in origin. To determine the pattern of topographic blocking, defined as a pattern that topography assumes when constrained by active forces other than erosion alone, low frequency passing spatial convolutions are used as filters and the resulting data are sliced into blocks according to pseudoelevations that produce a stable block pattern. The resultant blocks are analyzed according to its structural pattern of block size and block orientation. This analysis suggests that a topographic boundary cuts across the Mississippi embayment from near the Newport pluton on the west, to the area south of Memphis on east.« less
Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

NASA Astrophysics Data System (ADS)

Sauber, Jeanne M.; Molnia, Bruce F.

2004-07-01

Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes ( ML≥2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes ( Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake ( Ms=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass
Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

USGS Publications Warehouse

Sauber, J.M.; Molnia, B.F.

2004-01-01

Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes (ML???2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes (Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake (M s=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass
Wet Tectonics: A New Planetary Synthesis

NASA Astrophysics Data System (ADS)

Grimm, K. A.

2005-12-01

Most geoscientists (and geoscience textbooks) describe plate tectonics as a `solid-Earth' phenomenon, with fluids playing an important role in discrete geodynamic processes. As a community of diverse research specialists, the critical role of water is being widely elucidated, however these diverse studies do not address the fundamental origin and operation of the global plate tectonic phenomenon, and its expressions in planetary geodynamics and geomorphology. The Wet Tectonics hypothesis extends well beyond the plate tectonics paradigm, to constitute a new synthesis of diverse geoscience specializations and self-organizing complexity into a simple, internally consistent and explicitly testable model. The Wet Tectonics hypothesis asserts that Earth's plate tectonic system arose from and is the explicit and dynamic result of water interacting with the hot silicate mantle. The tectosphere is defined as an interactive functional (rather than structural, compositional or rheological) entity, a planetary-scale dynamic system of plate formation, plate motion, and rock/volatile recycling. Earth's tectosphere extends from the base of the asthenosphere to the top of the crust, arising and evolving as a dynamic pattern of organization that creates, orders and perpetuates itself. Earth's tectosphere is energetically-open, materially ajar (steady-state operation may not require sub-asthenospheric inputs; shifts between distinct tectonic modes may result from changes in coupling between the tectosphere and subasthenospheric reservoirs) and chemically-closed (i.e. the tectosphere recycles its own wastes). Water is a fundamental requirement in all of the constituent processes of Earth's tectosphere, including seafloor spreading, slab cooling/subsidence, plate motion, asthenosphere rheology, and subduction (where crustal and volatile recycling occur). As a working hypothesis, we suggest that the dynamic and persistent hydrosphere and tectosphere on planet Earth are fully
Polyphase tectonics at the southern tip of the Manila trench, Mindoro-Tablas Islands, Philippines

NASA Astrophysics Data System (ADS)

Marchadier, Yves; Rangin, Claude

1990-11-01

The southern termination of the Manila trench within the South China Sea continental margin in Mindoro is marked by a complex polyphase tectonic fabric in the arc-trench gap area. Onshore Southern Mindoro the active deformation front of the Manila trench is marked by parallel folds and thrusts, grading southward to N50° W-trending left-lateral strike-slip faults. This transpressive tectonic regime, active at least since the Late Pliocene, has overprinted the collision of an Early Miocene volcanic arc with the South China Sea continental margin (San Jose platform). The collision is postdated by deposition of the Late Miocene-Early Pliocene elastics of the East Mindoro basin. The tectonic and geological framework of this arc, which overlies a metamorphic basement and Eocene elastics, suggests that it was built on a drifted block of the South China Sea continental margin.
Escape tectonics and the extrusion of Alaska: Past, present, and future

USGS Publications Warehouse

Redfield, T.F.; Scholl, D. W.; Fitzgerald, P.G.; Beck, M.E.

2007-01-01

The North Pacific Rim is a tectonically active plate boundary zone parts of which may be characterized as a laterally moving orogenic stream. Crustal blocks are transported along large-magnitude strike-slip faults in western Canada and central Alaska toward the Aleutian-Bering Sea subduction zones. Throughout much of the Cenozoic, at and west of its Alaskan nexus, the North Pacific Rim orogenic Stream (NPRS) has undergone tectonic escape. During transport, relatively rigid blocks acquired paleomagnetic rotations and fault-juxtaposed boundaries while flowing differentially through the system, from their original point of accretion and entrainment toward the free face defined by the Aleutian-Bering Sea subduction zones. Built upon classical terrane tectonics, the NPRS model provides a new framework with which to view the mobilistic nature of the western North American plate boundary zone. ?? 2007 The Geological Society of America.
Venus: Mantle convection, hotspots, and tectonics

NASA Technical Reports Server (NTRS)

Phillips, R. J.

1989-01-01

The putative paradigm that planets of the same size and mass have the same tectonic style led to the adaptation of the mechanisms of terrestrial plate tectonics as the a priori model of the way Venus should behave. Data acquired over the last decade by Pioneer Venus, Venera, and ground-based radar have modified this view sharply and have illuminated the lack of detailed understanding of the plate tectonic mechanism. For reference, terrestrial mechanisms are briefly reviewed. Venusian lithospheric divergence, hotspot model, and horizontal deformation theories are proposed and examined.
Can deep seated gravitational slope deformations be activated by regional tectonic strain: First insights from displacement measurements in caves from the Eastern Alps

NASA Astrophysics Data System (ADS)

Baroň, Ivo; Plan, Lukas; Grasemann, Bernhard; Mitroviċ, Ivanka; Lenhardt, Wolfgang; Hausmann, Helmut; Stemberk, Josef

2016-04-01

Tectonic elastic strain and ground deformations are documented as the most remarkable environmental phenomena occurring prior to local earthquakes in tectonically active areas. The question arises if such strain would be able to trigger mass movements. We discuss a directly observed fault slip and a subsequent minor activation of a deep-seated gravitational slope deformation prior to the M = 3 Bad Fischau earthquake between end of November and early December 2013 in NE Austria. The data originate from two faults in the Emmerberg and Eisenstein Caves in the transition zone between the Eastern Alps and the Vienna Basin, monitored in the framework of the FWF "Speleotect" project. The fault slips have been observed at the micrometer-level by means of an opto-mechanical 3D crack gauge TM-71. The discussed event started with the fault activation in the Emmerberg Cave on 25 November 2013 recorded by measurements of about 2 μm shortening and 1 μm sinistral parallel slip, which was fully in agreement with the macroscopically documented past fault kinematics. One day later, the mass (micro) movement activated on the opposite side of the mountain ridge in the Eisenstein Cave and it continued on three consecutive days. Further, the fault in the Emmerberg Cave experienced also a subsequent gravitational relaxation on 2/3 December 2013, when the joint opened and the southern block subsided towards the valley, while the original sinistral displacement remained irreversible. The process was followed by the M = 3 earthquake in Bad Fischau on 11 December 2013. Our data suggest that tectonic strain could play a higher role on the activation of slow mass movements in the area than expected. Although we cannot fully exclude the co-activation of the mass movement in the Eisenstein Cave by water saturation, the presented data bring new insight into recent geodynamics of the Eastern Alps and the Vienna Basin. For better interpretations and conclusions however, we need a much longer
Topography of Venus and earth - A test for the presence of plate tectonics

NASA Technical Reports Server (NTRS)

Head, J. W.; Yuter, S. E.; Solomon, S. C.

1981-01-01

Comparisons of earth and Venus topography by use of Pioneer/Venus radar altimetry are examined. Approximately 93% of the Venus surface has been mapped with a horizontal resolution of 200 km and a vertical resolution of 200 m. Tectonic troughs have been indicated in plains regions which cover 65% of Venus, and hypsometric comparisons between the two planets' elevation distributions revealed that while the earth has a bimodal height distribution, Venus displays a unimodal configuration, with 60% of the planet surface within 500 m of the modal planet radius. The effects of mapping the earth at the same resolution as the Venus observations were explored. Continents and oceans were apparent, and although folded mountains appeared as high spots, no indications of tectonic activity were discernible. A NASA Venus Orbiting Imaging radar is outlined, which is designed to detect volcanoes, folded mountain ranges, craters, and faults, and thereby allow definition of possible plate-tectonic activity on Venus.
Imaging of the 3D crustal structure off the Joetsu region in Japan Sea and its implication of the activity of the tectonic zone by using LT-OBSs

NASA Astrophysics Data System (ADS)

Machida, Y.; Shinbo, T.; Shinohara, M.; Yamada, T.; Mochizuki, K.; Kanazawa, T.

2011-12-01

At the eastern margin of the Japan Sea, large earthquakes have been occurred (e.g., 1964 Niigata earthquake, the 1983 Japan Sea earthquake, the 2004 Chuetsu earthquake and the 2007 Chuetsu-oki earthquake) along the Niigata-Kobe Tectonic Zone (NKTZ). The NKTZ is recognized as a region of large strain rate along the Japan Sea coast and in the northern Chubu and Kinki distinct. Among these events, the 2004 Chuetsu earthquake and the 2007 Chuetsu-oki earthquake is triggered by reactivation of pre-existing faults within ancient rift systems by stress loading through a ductile creeping of the weak lower crust (Kato et al., 2008). Because a source region of the 2007 Chuetsu-oki earthquake is distributed under the Japan Sea, aftershock observation using Ocean Bottom Seismometers were carried out (Shinohara et al., 2008). It is necessary to estimate precise aftershock distribution in order to understand the mechanism of earthquake generation. In addition, a seismic refraction survey was carried out to reveal crustal structure in the region (Nakahigashi et al., submitted). They indicated that most of aftershocks were occurred in the upper crust. Because the tectonic zone is thought to be spread in offshore region, it is difficult to understand a precise activity of the tectonic zone from only land-base observations. To compare the seismic activity with the crustal structure in the region is indispensable to understand the stress field in the tectonic zone and the tectonics in the eastern margin of the Japan Sea. In order to investigate a seismic activity in the tectonic zone, 10 Long-Term Ocean Bottom Seismometers (LT-OBS) were deployed from December, 2008, to October, 2009, in the off Joetsu region. First we estimated hypocenters of events using a location program for finding a maximum likelihood solution using a Bayesian approach (Hirata and Matsu'ura, 1987). The velocity structure for the location was modeled from a previous refraction survey conducted in the same region

Tectonics and Volcanism During the Cretaceous Normal Superchron Seafloor in the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

O'Brien, E.

2017-12-01

We have conducted an integration study on the origin and evolution of the tectonics and volcanism of seafloor in the Western Pacific Ocean that took place during the Cretaceous Normal Superchron (CNS) where sparse data has so far precluded detailed investigation. We have compiled the latest satellite-based gravity, gravity gradient, and magnetic grids (EMAG2 v.3) for this region. These crustal-scale high-resolution grids suggest that the CNS seafloor contains fossilized lithospheric morphology possibly attributed to the interaction between Cretaceous supervolcanism activity and Mid-Cretaceous Pacific mid ocean ridge systems that have continuously expanded the Pacific Plate. We recognize previously identified fossilized microplates west of the Magellan Rise, short-lived abandoned propagating rifts and fracture zones, all of which show significant rotation of seafloor fabric. In addition to these large scale observations, we have also compiled marine geological information from previously drilled cores and new data from a Kongsberg Topas PS18 Parametric Sub-Bottom Profiler collected on a transect from Honolulu, Hawaii to Apra, Guam acquired during research cruise SKQ2014S2. In particular, the narrow beam and high bandwidth signal of the Topas PS18 sub-bottom profiler provides sonar data of the seabed with a resolution and depth penetration that is unprecedented compared with previously available surveys in the region. A preliminary assessment of this high resolution Topas data allows us to better characterize sub-seafloor sediment properties and identify features, including the Upper Transparent Layer with identifiable pelagic clay and porcelanite-chert reflectors as well as tectonic features such as the westernmost tip of the Waghenaer Fracture Zone.
Learning Plate Tectonics Using a Pre-Analogy Step

NASA Astrophysics Data System (ADS)

Glesener, G. B.; Sandoval, W. A.

2011-12-01

Previous research has shown that children tend to demonstrate lower performance on analogical reasoning tasks at a causal relations level compared to most adults (Gentner & Toupin, 1986). This tendency is an obstacle that geoscience educators must overcome because of the high frequency of analogies used in geoscience pedagogy. In particular, analog models are used to convey complex systems of non-everyday/non-observable events found in nature, such as plate tectonics. Key factors in successful analogical reasoning that have been suggested by researchers include knowledge of the causal relations in the base analog (Brown & Kane, 1988; Gentner, 1988; Gentner & Toupin, 1986), and development of learning strategies and metaconceptual competence(Brown & Kane, 1988). External factors, such as guiding cues and hints have been useful cognitive supports that help students reason through analogical problems (Gick & Holyoak, 1980). Cognitive supports have been seen by researchers to decrease processing demands on retrieval and working memory (Richland, Zur, & Holyoak, 2007). We observed third and fourth graders learning about plate tectonics beginning with a pre-analogy step-a cognitive support activity a student can do before working with an analogy to understand the target. This activity was designed to aid students in developing their understanding of object attributes and relations within an analog model so that more focus can be placed on mapping the corresponding higher-order relations between the base and target. Students learned targeted concepts of plate tectonics, as measured by pre to post gains on items adapted from the Geosciences Concept Inventory. Analyses of classroom interaction showed that students used the object attributes and higher-order relations highlighted in the pre-analogy activity as resources to reason about plate boundaries and plate movement during earthquakes.
Facies Analysis of the Tandoǧdu Travertines, Van, Eastern Anatolia, Turkey: implications for the active tectonic deformation behind the formation and evolution of the travertines

NASA Astrophysics Data System (ADS)

Yesilova, Cetin; Yesilova, Pelin; Aclan, Mustafa; Gülyüz, Nilay

2017-04-01

In this study, stratigraphic and sedimentologic characteristics of Tandoǧdu travertines exposing at the 13 km southwest of Başkale, Van were examined. In this respect, we shed light on their formation conditions and depositional environment by determining their morphological characteristics and analyzing their facies distribution. In addition, kinematic studies were conducted by collecting structural data from the structures hosting the travertines. Tandoǧdu travertines having bed type and ridge type travertines have 5 distinct lithofacies based on the studies conducted. These are: (1) crystalline crust facies, (2) coated bubble facies, (3) paper-thin raft type facies, (4) lithoclast - breccia facies and (5) paleosoil facies. According to the examination of their morphologies and lithofacies; lithofacies were developed depending on the temperature of fluids forming the travertines. Distal from the source field of the hydrothermal fluids, paper-thin raft type facies were developed in shallow pools. Proximal to the source field of the hydrothermal fluids, crystalline crust facies and coated bubble facies were deposited. Existence of breccia facies indicates the effects of active tectonism during the formation of travertines. Hot hydrothermal pools on the ridge type travertines prove the still active tectonic activities. On-going studies aim to date growth of the travertines by U-Th dating method which will also shed some light on the tectonic scenario behind the evolution of the travertines.
Playing jigsaw with Large Igneous Provinces—A plate tectonic reconstruction of Ontong Java Nui, West Pacific

NASA Astrophysics Data System (ADS)

Hochmuth, Katharina; Gohl, Karsten; Uenzelmann-Neben, Gabriele

2015-11-01

The three largest Large Igneous Provinces (LIP) of the western Pacific—Ontong Java, Manihiki, and Hikurangi Plateaus—were emplaced during the Cretaceous Normal Superchron and show strong similarities in their geochemistry and petrology. The plate tectonic relationship between those LIPs, herein referred to as Ontong Java Nui, is uncertain, but a joined emplacement was proposed by Taylor (2006). Since this hypothesis is still highly debated and struggles to explain features such as the strong differences in crustal thickness between the different plateaus, we revisited the joined emplacement of Ontong Java Nui in light of new data from the Manihiki Plateau. By evaluating seismic refraction/wide-angle reflection data along with seismic reflection records of the margins of the proposed "Super"-LIP, a detailed scenario for the emplacement and the initial phase of breakup has been developed. The LIP is a result of an interaction of the arriving plume head with the Phoenix-Pacific spreading ridge in the Early Cretaceous. The breakup of the LIP shows a complicated interplay between multiple microplates and tectonic forces such as rifting, shearing, and rotation. Our plate kinematic model of the western Pacific incorporates new evidence from the breakup margins of the LIPs, the tectonic fabric of the seafloor, as well as previously published tectonic concepts such as the rotation of the LIPs. The updated rotation poles of the western Pacific allow a detailed plate tectonic reconstruction of the region during the Cretaceous Normal Superchron and highlight the important role of LIPs in the plate tectonic framework.
Magma-Tectonic Interactions along the Central America Volcanic Arc: Insights from the August 1999 Magmatic and Tectonic Event at Cerro Negro, Nicaragua

NASA Astrophysics Data System (ADS)

La Femina, P.; Connor, C.; Strauch, W.

2002-12-01

Volcanic vent alignments form parallel to the direction of maximum horizontal stress, accommodating extensional strain via dike injection. Roughly east-west extension within the Central America Volcanic Arc is accommodated along north-northwest-trending basaltic vent alignments. In Nicaragua, these alignments are located in a northwest-trending zone of dextral shear, with shear accommodated along northeast trending bookshelf faults. The recent eruption of Cerro Negro volcano, Nicaragua and Marabios Range seismic swarm revealed the interaction of these fault systems. A low energy (VEI 1), small volume (0.001 km3 DRE) eruption of highly crystalline basalt occurred at Cerro Negro volcano, Nicaragua, August 5-7, 1999. This eruption followed three tectonic earthquakes (each Mw 5.2) in the vicinity of Cerro Negro hours before the onset of eruptive activity. The temporal and spatial pattern of microseismicity and focal mechanisms of the Mw 5.2 earthquakes suggests the activation of northeast-trending faults northwest and southeast of Cerro Negro within the Marabios Range. The eruption was confined to three new vents formed on the southern flank of Cerro Negro along a preexisting north-northwest trending alignment; the El Hoyo alignment of cinder cones, maars and explosion craters. Surface ruptures formed > 1 km south and southeast of the new vents suggest dike injection. Numerical simulations of conduit flow illustrate that the observed effusion rates (up to 65 ms-1) and fountain heights (50-300 m) can be achieved by eruption of magma with little or no excess fluid pressure, in response to tectonic strain. These observations and models suggest that 1999 Cerro Negro activity is an excellent example of tectonically induced small-volume eruptions in an arc setting.
Tectonics and metallogenic provinces

USGS Publications Warehouse

Guild, P.W.

1983-01-01

Various theories have been advanced to explain the well-known uneven distribution of metals and ore-deposit types in space and time. Primordial differences in the mantle, preferential concentration of elements in the crust, the prevalence of ore-forming processes at certain times and (or) places, and combinations of one or several of these factors have all been called upon to account for the "metallogenic provinces," which can be defined loosely as regions containing similar deposits of one or a group of metals or minerals. Because many, perhaps most, provinces have complex, multistage origins, the relative importance of inheritance vs. process is still controversial. In recent years the geographic relationship of many geologically young provinces to present-day plate-tectonic positions (accreting or consuming margins, intraplate structures, etc.) has been widely recognized, and the presumption is strong that older provinces had similar relationships to former plates. As most ore deposits resulted from a favorable conjunction of geological processes that are no longer operative, elucidation of their genesis requires reconstruction of the geologic history of the province, with particular emphasis on events coeval with mineralization. Tectonic analysis is an important aspect of this reconstruction; data from orbiting satellites have contributed greatly to this analysis, as the voluminous literature of the past decade testifies. Both the synoptic view of large areas and the ability to emphasize faint contrasts have revealed linear, curvilinear, and circular features not previously recognized from field studies. Some of these undoubtedly reflect basement structures that have contributed to the development, or limit the extent, of metallogenic provinces. Their recognition and delineation will be increasingly valuable to the assessment of resources available and as guides to exploration for the ores needed by future generations. ?? 1983.
Prototypical Concepts and Misconceptions of Plate Tectonic Boundaries

NASA Astrophysics Data System (ADS)

Sibley, D. F.; Patino, L. C.

2003-12-01

Students of geology encounter many prototypical/exemplar concepts* that include representative, but not necessarily defining, features and characteristics. This study of students' prototypical representations of plate tectonic boundaries indicates that their representations are rich sources of information about their misconceptions about plate tectonics. After lectures in plate tectonics and mountain building, 353 students in a general education geology class were asked to draw a continent-continent convergent boundary. For this study, a correct answer is defined as having the major features in correct proportions as depicted in the plate boundary diagrams on the USGS web. Fifty-two percent of the drawings were either incorrect or incomplete such that they could not be interpreted. Only 48% were readily interpretable, and of these 22% drew the boundary correctly, showing a thickening of crust where two continents collide. Thirty-three percent drew the boundary showing concave slabs of continental crust as one might imagine two pieces of firm rubber pushed together on a rigid surface and 45% depicted mountains as one might imagine inverted ice cream cones on a rigid plank. Twenty-one senior class geology majors and graduate students were given the same assignment. Forty-eight percent rendered a correct drawing, whereas 38% drew the same ice cream cone on a plank type picture that 45% of the general education students drew. In a second class of 12 geology majors, only 1 student drew a cross section of a continent-ocean boundary similar to standard representation. Four of 12 drew mountains on the top of continental crust over a subduction zone but did not draw a compensating mass within the crust or lithosphere. Prototypical drawings provide more information about students' concepts than do most multiple-choice questions. For example, sixty-two percent of theses students who drew mountains similar to foam rubber pads pushed together on a desk or ice cream cones on a
DELP Symposium: Tectonics of eastern Asia and western Pacific Continental Margin

NASA Astrophysics Data System (ADS)

Eastern Asia and the western Pacific make up a broad region of active plate tectonic interaction. The area is a natural laboratory for studying the processes involved in the origin and evolution of volcanic island arcs, marginal basins, accretionary prisims, oceanic trenches, accreted terranes, ophiolite emplacement, and intracontinental deformation. Many of our working concepts of plate tectonics and intraplate deformation were developed in this region, even though details of the geology and geophysics there must be considered of a reconnaissance nature.During the past few years researchers have accumulated a vast amount of new and detailed information and have developed a better understanding of the processes that have shaped the tectonic elements in this region. To bring together scientists from many disciplines and to present the wide range of new data and ideas that offer a broader perspective on the interrelations of geological, geochemical, geophysical and geodetic studies, the symposium Tectonics of Eastern Asia and Western Pacific Continental Margin was held December 13-16, 1988, at the Tokyo Institute of Technology in Japan, under the auspicies of DELP (Dynamics and Evolution of the Lithosphere Project).
A transparent and data-driven global tectonic regionalization model for seismic hazard assessment

NASA Astrophysics Data System (ADS)

Chen, Yen-Shin; Weatherill, Graeme; Pagani, Marco; Cotton, Fabrice

2018-05-01

A key concept that is common to many assumptions inherent within seismic hazard assessment is that of tectonic similarity. This recognizes that certain regions of the globe may display similar geophysical characteristics, such as in the attenuation of seismic waves, the magnitude scaling properties of seismogenic sources or the seismic coupling of the lithosphere. Previous attempts at tectonic regionalization, particularly within a seismic hazard assessment context, have often been based on expert judgements; in most of these cases, the process for delineating tectonic regions is neither reproducible nor consistent from location to location. In this work, the regionalization process is implemented in a scheme that is reproducible, comprehensible from a geophysical rationale, and revisable when new relevant data are published. A spatial classification-scheme is developed based on fuzzy logic, enabling the quantification of concepts that are approximate rather than precise. Using the proposed methodology, we obtain a transparent and data-driven global tectonic regionalization model for seismic hazard applications as well as the subjective probabilities (e.g. degree of being active/degree of being cratonic) that indicate the degree to which a site belongs in a tectonic category.
Global-scale tectonic patterns on Pluto

NASA Astrophysics Data System (ADS)

Matsuyama, I.; Keane, J. T.; Kamata, S.

2016-12-01

The New Horizons spacecraft revealed a global-scale tectonic pattern on the surface of Pluto which is presumably related to its formation and early evolution. Changes in the rotational and tidal potentials, expansion, and loading can generate stresses capable of producing global-scale tectonic patterns. The current alignment of Sputnik Planum with the tidal axis suggests a reorientation of Pluto relative to the rotation and tidal axes, or true polar wander. This reorientation can be driven by mass loading associated with Sputnik Planum. We developed a general theoretical formalism for the calculation of tectonic patterns due to a variety of process including true polar wander, loading, and expansion. The formalism is general enough to be applicable to non-axisymmetric loads. We illustrate that the observed global-scale tectonic pattern can be explained by stresses generated by true polar wander, Sputnik Planum loading, and expansion.
Diffuse Extension of the Southern Mariana Margin: Implications for Subduction Zone Infancy and Plate Tectonics

NASA Astrophysics Data System (ADS)

Martinez, F.; Stern, R. J.; Kelley, K. A.; Ohara, Y.; Sleeper, J. D.; Ribeiro, J. M.; Brounce, M. N.

2017-12-01

Opening of the southern Mariana margin takes place in contrasting modes: Extension normal to the trench forms crust that is passively accreted to a rigid Philippine Sea plate and forms along focused and broad accretion axes. Extension also occurs parallel to the trench and has split apart an Eocene-Miocene forearc terrain accreting new crust diffusely over a 150-200 km wide zone forming a pervasive volcano-tectonic fabric oriented at high angles to the trench and the backarc spreading center. Earthquake seismicity indicates that the forearc extension is active over this broad area and basement samples date young although waning volcanic activity. Diffuse formation of new oceanic crust and lithosphere is unusual; in most oceanic settings extension rapidly focuses to narrow plate boundary zones—a defining feature of plate tectonics. Diffuse crustal accretion has been inferred to occur during subduction zone infancy, however. We hypothesize that, in a near-trench extensional setting, the continual addition of water from the subducting slab creates a weak overriding hydrous lithosphere that deforms broadly. This process counteracts mantle dehydration and strengthening proposed to occur at mid-ocean ridges that may help to focus deformation and melt delivery to narrow plate boundary zones. The observations from the southern Mariana margin suggest that where lithosphere is weakened by high water content narrow seafloor spreading centers cannot form. These conditions likely prevail during subduction zone infancy, explaining the diffuse contemporaneous volcanism inferred in this setting.
Tectonic Impact on the Sedimentary Magnetic Record in Active Margin Settings

NASA Astrophysics Data System (ADS)

Riedinger, N.; Torres, M. E.; Solomon, E. A.

2017-12-01

Here we explore the impact of depositional and tectonic dynamics on sedimentary magnetic signals using samples collected during the Integrated Ocean Drilling Project (IODP) Expedition 334 off Costa Rica. This active margin system displays fast convergence rates, abundant seismicity, and subduction erosion, and thus allows us to study fluid flow responses to rapid episodes of uplift and subsidence in an erosional convergent margin - one of the main goals of the Costa Rica Seismogenesis Project (CRISP). The sediments at the middle slope site (Site U1378; 533 m water depth) vary strongly in their magnetic susceptibility and geochemical signals compared to the upper slope site (Site U1379; 139 m water depth). The more recent sediments at each site (upper 50 m) clearly show that Site U1378 experienced relative steady state conditions (with respect to pore water geochemistry), while at Site U1379 dynamic conditions lead to non-steady state geochemical profiles - and consequently to a differing magnetic susceptibility profile. These differences are most likely related to changes in methane flux and subsequent shifting of the sulfate-methane transition. Throughout the sediment column at Hole U1379C intervals showing a strong decrease in the magnetic susceptibility can be correlated with specific lithological horizons with abundant carbonate layers. Our data show that these layers are formed diagenetically, based on a depleted carbonate carbon isotope signal (up to -25‰) that is consistent with the pore water record. The carbonate layers not only caused a dilution in the magnetic mineral assemblages, but also point to a concurrent alteration process of iron oxides to iron sulfides. This is recorded in the sedimentary record as iron sulfide (pyrite) enrichments and their associated sulfur isotopic signature (δ34S; up to +6.3‰). These alterations can be tied to a location fluctuation of the sulfate-methane transition due to changes in the methane flux. The strong
Bathymetry of the Levant basin: interaction of salt-tectonics and surficial mass movements

NASA Astrophysics Data System (ADS)

Gvirtzman, Zohar; Reshef, Moshe; Buch-Leviatan, Orna; Groves-Gidney, Gavrielle; Karcz, Zvi; Makovsky, Yizhaq; Ben-Avraham, Zvi

2015-04-01

A new high resolution bathymetric map of the Levant Basin between Israel and the Eratosthenes Seamount reveals previously undetected folds, faults and channels. The map facilitates a regional map-view analysis of structures that were previously examined only in cross section. The systematic mapping of morpho-structural elements in the entire basin is followed by a kinematic interpretation that distinguished between two main processes sculpting the seabed from bottom and top: salt tectonics and sediment transport. We show that the contractional domain related to salt tectonics is far more complex than previously thought. Ridges, previously interpreted as contractional folds are, in fact, surficial undulations of the seabed reminiscent of sediment waves. Moreover, other folds previously interpreted as downdip contraction of the westward gliding Plio-Quaternary section are, in some parts of the basin, caused by updip climbing of this section eastwards as a result of the regional pattern of salt flow away from the Nile Cone. In the context of sediment transport, we show that the northern Sinai continental slope is covered by a dense net of turbidite channels, whereas the Levant slope has no channels at all. Particularly interesting is the Levant Turbidite Channel, described and named here for the first time. This feature begins at the southeastern corner of the Mediterranean at water depths of ~1100 m, continues along the valley between the Sinai and Levant slopes, and reaches the deepest part of the basin, in water depths of ~2500 m, northeast of the Eratosthenes seamount. However, this prominent feature cannot be explained by the current drainage, consisting of two minor rivers that enter the basin at that point, and thus most likely reflects periods of wetter climate and/or lower sea-level, when these rivers were more active and possibly connected to the submarine channel system.
Quaternary Tectonic and Climatic Processes shaping the Central Andean hyperarid forearc (southern Peru)

NASA Astrophysics Data System (ADS)

Audin, Laurence; Benavente, Carlos; Zerathe, Swann; Saillard, Marianne; Hall, Sarah R.; Farber, Daniel L.

2015-04-01

Understanding the forearc structure and processes related to Quaternary evolution and uplift of the Western Andean Cordillera remains an outstanding scientific issue. Models of Andean Plateau evolution based on Tertiary volcanic stratigraphy since 5Ma suggest that the deformation was focused along the eastern margin of the plateau and that minimal uplift occurred along the Pacific margin. On the contrary, new tectonic data and Quaternary surface 10Be dating highlight the presence of recently active deformation, incision and alluvial processes within the upper Andean forearc together with a regional uplift of the coastal zone. Additionally, the high obliquity observed in the northern Arica Bend region makes it an ideal target to discuss whether partitioning of the oblique convergence is accommodated by the neotectonic features that dissect the Quaternary forearc. Our goals are both to decipher the Quaternary tectonic and climatic processes shaping the hyperarid forearc along strike and across strike. Finally, we aim to quantify the respective influence of these factors in the overall uplift of the Western Andes. Indeed, sequences of pediment surfaces, landslide products, paleolake deposits and marine terraces found along the oblique Peruvian margin are a unique set of datable markers that can be used to quantify the rates of Quaternary processes. In this study, we focus on the southern Peru hyperarid Atacama area where regional surfaces and tectonic markers (scarps, folds, temporary streams and paleolake levels offsets…) are well preserved for the Quaternary timescale. Numerous landsliding events align on the major fault segments and reflect Plio-Pleistocene climatic and tectonic activity together with filled and strath terraces. As the present day sea-level is one of the highest levels recorded for Quaternary time span, any emerged marine terrace is preserved by tectonic coastal uplift. In particular, the geomorphic and chronologic correlation between marine and
Paleomagnetic and Tectonic studies in Uruguay: a brief synthesis of the last decade

NASA Astrophysics Data System (ADS)

Sanchez Bettucci, L.

2013-05-01

The paleomagnetic studies in Uruguay have been applied as a complementary tool to geological studies. Paleomagnetic data can be very useful for geodynamic reconstructions, fundamentally for determine the latitudinal tectonic transport, rotations of crustal blocks. This technique has been applied to Paleoproterozoic, Neoproterozoic and Paleozoic units. The geology of the Uruguayan territory is divided into four tectonic units of Uruguay that include a) the Piedra Alta tectonostratigraphic terrane (PATT) and b) Nico Pérez tectonostratigraphic terrane (NPTT), separated by the Sarandí del Yí high-strain zone. Both terranes are well exposed in the Río de La Plata craton (RPC) and have paleoproterozoic ages, the last was reworked in Neoproterozoic times (metacraton). The most thoroughly investigated Neoproterozoic sections are located in the eastern and southeastern regions of Uruguay. The c) Dom Feliciano Belt shows a tectonic evolution from back-arc to foreland basin characterized by fold-and-thrust, thick-skinned belts developed during the Brasiliano/Pan-African orogenic cycle. And finally d) The high metamorphic grade Punta del Este terrane where its most notable feature is their African affinity. There is a significant shortage of geochemical and geochronological data for the existing geological complexity.
History and Evolution of Precambrian plate tectonics

NASA Astrophysics Data System (ADS)

Fischer, Ria; Gerya, Taras

2014-05-01

Plate tectonics is a global self-organising process driven by negative buoyancy at thermal boundary layers. Phanerozoic plate tectonics with its typical subduction and orogeny is relatively well understood and can be traced back in the geological records of the continents. Interpretations of geological, petrological and geochemical observations from Proterozoic and Archean orogenic belts however (e.g., Brown, 2006), suggest a different tectonic regime in the Precambrian. Due to higher radioactive heat production the Precambrian lithosphere shows lower internal strength and is strongly weakened by percolating melts. The fundamental difference between Precambrian and Phanerozoic tectonics is therefore the upper-mantle temperature, which determines the strength of the upper mantle (Brun, 2002) and the further tectonic history. 3D petrological-thermomechanical numerical modelling experiments of oceanic subduction at an active plate at different upper-mantle temperatures show these different subduction regimes. For upper-mantle temperatures < 175 K above the present day value a subduction style appears which is close to present day subduction but with more frequent slab break-off. At upper-mantle temperatures 175 - 250 K above present day values steep subduction continues but the plates are weakened enough to allow buckling and also lithospheric delamination and drip-offs. For upper-mantle temperatures > 250 K above the present day value no subduction occurs any more. The whole lithosphere is delaminating and due to strong volcanism and formation of a thicker crust subduction is inhibited. This stage of 200-250 K higher upper mantle temperature which corresponds roughly to the early Archean (Abbott, 1994) is marked by strong volcanism due to sublithospheric decompression melting which leads to an equal thickness for both oceanic and continental plates. As a consequence subduction is inhibited, but a compressional setup instead will lead to orogeny between a continental
Creep of phyllosilicates at the onset of plate tectonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amiguet, Elodie; Reynard, Bruno; Caracas, Razvan

Plate tectonics is the unifying paradigm of geodynamics yet the mechanisms and causes of its initiation remain controversial. Some models suggest that plate tectonics initiates when the strength of lithosphere is lower than 20-200 MPa, below the frictional strength of lithospheric rocks (>700 MPa). At present-day, major plate boundaries such as the subduction interface, transform faults, and extensional faults at mid-oceanic ridge core complexes indicate a transition from brittle behaviour to stable sliding at depths between 10 and 40 km, in association with water-rock interactions forming phyllosilicates. We explored the rheological behaviour of lizardite, an archetypal phyllosilicate of the serpentinemore » group formed in oceanic and subduction contexts, and its potential influence on weakening of the lithospheric faults and shear zones. High-pressure deformation experiments were carried out on polycrystalline lizardite - the low temperature serpentine variety - using a D-DIA apparatus at a variety of pressure and temperature conditions from 1 to 8 GPa and 150 to 400 C and for strain rates between 10{sup -4} and 10{sup -6} s{sup -1}. Recovered samples show plastic deformation features and no evidence of brittle failure. Lizardite has a large rheological anisotropy, comparable to that observed in the micas. Mechanical results and first-principles calculations confirmed easy gliding on lizardite basal plane and show that the flow stress of phyllosilicate is in the range of the critical value of 20-200 MPa down to depths of about 200 km. Thus, foliated serpentine or chlorite-bearing rocks are sufficiently weak to account for plate tectonics initiation, aseismic sliding on the subduction interface below the seismogenic zone, and weakening of the oceanic lithosphere along hydrothermally altered fault zones. Serpentinisation easing the deformation of the early crust and shallow mantle reinforces the idea of a close link between the occurrence of plate tectonics and
Tectonic asymmetry of the earth and other planets

NASA Technical Reports Server (NTRS)

Pushcharovskiy, Y. M.; Kozlov, V. V.; Sulidi-Kondratyev, Y. D.

1978-01-01

The structures of Earth, Mars, Venus, and the Moon are examined and compared. Global tectonic characteristics are presented for each. A comparison of the tectonics reveals the structural asymetry of these planets and the moon. Tectonic asymmetry information for the group is used to interpret certain aspects of the earth's geological past.
Tectonics of the Kızılırmak Delta and Sinop Basin, offshore Pontides, evidence from new, high resolution seismic and bathymetric data.

NASA Astrophysics Data System (ADS)

Haşimoğlu, B. Y.; Cifci, G.; Lacassin, R.; Fernández-Blanco, D.; Ozel, O.

2016-12-01

The Kızılırmak River is the one of the largest river in Turkey, flowing across two key features characteristic of the Late Cenozoic tectonic evolution of Northern Turkey: the North Anatolian Fault and the Pontides. The offshore part of the fan delta of the Kızılırmak river is of particular interest, since it contains valuable information on the 3D delta structure directly related to the river dynamics, and encompasses essential tectonic and bathymetric features like the Sinop graben and Archangelsky ridge. We present new high-resolution multichannel seismic data and multibeam bathymetric data that have been collected in this area by researchers and PhD/MSc students of Dokuz Eylül University, Institute of Marine Sciences and Technology with R/V Koca Piri Reis. 17 seismic lines, for a total of 1300km, have been acquired and processed in order to enhance the visualization of the stratigraphy and of tectonic structures, and to remove multiples. In our preliminary interpretation of the seismic data we observe a thick pile of sediments of probable upper Cenozoic age lying of top of an erosional surface possibly related to the Messinian salinity crisis or to older events. These sediments are affected both by gravitational processes and by normal faulting, related to the actively growing Sinop graben. The Archangelsky ridge is well resolved down to 3-4s and appears to be bounded by active normal faults and likely crosscut by strike-slip faults. Our bathymetric data reveals the submarine channel of the Yeşilırmak river, which connects to the paleo streambed of the Kızılırmak river. This is the first high resolution seismic dataset that has been collected in this area, and in our ongoing study we aim at integrating this state-of-the-art new data with the onshore evolution of the Kızılırmak delta. This will potentially bring a valuable new perspective to reconcile sedimentation rates and the offshore delta-architecture with the onshore delta dynamics, and can
Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone-Ganga alluvial tract in Middle Ganga Plain, India

NASA Astrophysics Data System (ADS)

Sahu, Sudarsan; Saha, Dipankar

2014-08-01

The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone-Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur-Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width-depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE-SW direction.

This dynamic earth: the story of plate tectonics

USGS Publications Warehouse

Kious, W. Jacquelyne; Tilling, Robert I.

1996-01-01

In the early 1960s, the emergence of the theory of plate tectonics started a revolution in the earth sciences. Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes. We now know that, directly or indirectly, plate tectonics influences nearly all geologic processes, past and present. Indeed, the notion that the entire Earth's surface is continually shifting has profoundly changed the way we view our world.People benefit from, and are at the mercy of, the forces and consequences of plate tectonics. With little or no warning, an earthquake or volcanic eruption can unleash bursts of energy far more powerful than anything we can generate. While we have no control over plate-tectonic processes, we now have the knowledge to learn from them. The more we know about plate tectonics, the better we can appreciate the grandeur and beauty of the land upon which we live, as well as the occasional violent displays of the Earth's awesome power.This booklet gives a brief introduction to the concept of plate tectonics and complements the visual and written information in This Dynamic Planet (see Further reading), a map published in 1994 by the U.S. Geological Survey (USGS) and the Smithsonian Institution. The booklet highlights some of the people and discoveries that advanced the development of the theory and traces its progress since its proposal. Although the general idea of plate tectonics is now widely accepted, many aspects still continue to confound and challenge scientists. The earth-science revolution launched by the theory of plate tectonics is not finished.
Developing an Education and Public Outreach (EPO) program for Caltech's Tectonics Observatory

NASA Astrophysics Data System (ADS)

Kovalenko, L.; Jain, K.; Maloney, J.

2012-12-01

The Caltech Tectonics Observatory (TO) is an interdisciplinary center, focused on geological processes occurring at the boundaries of Earth's tectonic plates (http://www.tectonics.caltech.edu). Over the past four years, the TO has made a major effort to develop an Education and Public Outreach (EPO) program. Our goals are to (1) inspire students to learn Earth Sciences, particularly tectonic processes, (2) inform and educate the general public about science in the context of TO discoveries, and (3) provide opportunities for graduate students, postdocs, and faculty to do outreach in the local K-12 schools and community colleges. Our work toward these goals includes hosting local high school teachers and students each summer for six weeks of research experience (as part of Caltech's "Summer Research Connection"); organizing and hosting an NAGT conference aimed at Geoscience teachers at community colleges; participating in teacher training workshops (organized by the local school district); hosting tours for K-12 students from local schools as well as from China; and bringing hands-on activities into local elementary, middle, and high school classrooms. We also lead local school students and teachers on geology field trips through nearby canyons; develop education modules for undergraduate classes (as part of MARGINS program); write educational web articles on TO research (http://www.tectonics.caltech.edu/outreach/highlights/), and regularly give presentations to the general public. This year, we started providing content expertise for the development of video games to teach Earth Science, being created by GameDesk Institute. And we have just formed a scientist/educator partnership with a 6th grade teacher, to help in the school district's pilot program to incorporate new national science standards (NSTA's Next Generation Science Standards, current draft), as well as use Project-Based Learning. This presentation gives an overview of these activities.
Teaching Tectonics to Undergraduates with Web GIS

NASA Astrophysics Data System (ADS)

Anastasio, D. J.; Bodzin, A.; Sahagian, D. L.; Rutzmoser, S.

2013-12-01

Geospatial reasoning skills provide a means for manipulating, interpreting, and explaining structured information and are involved in higher-order cognitive processes that include problem solving and decision-making. Appropriately designed tools, technologies, and curriculum can support spatial learning. We present Web-based visualization and analysis tools developed with Javascript APIs to enhance tectonic curricula while promoting geospatial thinking and scientific inquiry. The Web GIS interface integrates graphics, multimedia, and animations that allow users to explore and discover geospatial patterns that are not easily recognized. Features include a swipe tool that enables users to see underneath layers, query tools useful in exploration of earthquake and volcano data sets, a subduction and elevation profile tool which facilitates visualization between map and cross-sectional views, drafting tools, a location function, and interactive image dragging functionality on the Web GIS. The Web GIS platform is independent and can be implemented on tablets or computers. The GIS tool set enables learners to view, manipulate, and analyze rich data sets from local to global scales, including such data as geology, population, heat flow, land cover, seismic hazards, fault zones, continental boundaries, and elevation using two- and three- dimensional visualization and analytical software. Coverages which allow users to explore plate boundaries and global heat flow processes aided learning in a Lehigh University Earth and environmental science Structural Geology and Tectonics class and are freely available on the Web.
The evolution of tectonic features on Ganymede

NASA Technical Reports Server (NTRS)

Squyres, S. W.

1982-01-01

The bands of bright resurfaced terrain on Ganymede are probably broad grabens formed by global expansion and filled with deposits of ice. Grooves within the bands are thought to be extensional features formed during the same episode of expansion. The crust of Ganymede is modeled as a viscoelastic material subjected to extensional strain. With sufficiently high strain rates and stresses, deep normal faulting will occur, creating broad grabens that may then be filled. Continuing deformation at high strain rates and stresses will cause propagation of deep faults up into the flood deposits and normal faulting at the surface, while lower strain rates and stresses will cause formation of open extension fractures or, if the crustal strength is very low, grabens at the surface. The spacing between adjacent fractures may reflect the geothermal gradient at the time of deformation. Surface topography resulting from fracturing and normal faulting will decay with time as a result of viscous relaxation and mass-wasting.
Paleozoic intrusive rocks from the Dunhuang tectonic belt, NW China: Constraints on the tectonic evolution of the southernmost Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Zhao, Yan; Sun, Yong; Diwu, Chunrong; Zhu, Tao; Ao, Wenhao; Zhang, Hong; Yan, Jianghao

2017-05-01

those Paleozoic intrusive rocks reveal that both the Silurian and the late Devonian magmatic activities predominantly represent crustal growth processes in the DTB, accompanied by different degrees of reworking of pre-existing continental crust. However, the middle Carboniferous (ca. 335-315 Ma) magmatic activity reflects a crustal reworking process. The Silurian and late Devonian intrusive rocks were most likely formed in the arc-related subduction zones, whereas, the middle Carboniferous intrusive rocks were possibly formed in a transitional tectonic setting from compression to extension, representing the final stage of Paleozoic orogeny in the DTB. These Paleozoic magmatic rocks further suggest that the DTB has reactivated from a stable block to an orogen and undergone two episodes (the early Paleozoic and the late Paleozoic) of orogeny during Paleozoic. It represents a Paleozoic accretionary orogen of the southernmost margin of the CAOB between the Tarim Craton and North China Craton, and tectonically extends northward to the Beishan orogen and westward to the eastern South Tianshan Belt.
Tectonic interpretation of the 13 february 2001, mw 6.6, El Salvador Earthquake: New evidences of coseismic surface rupture and paleoseismic activity.

NASA Astrophysics Data System (ADS)

Martinez-Diaz, J. J.; Canora, C.; Villamor, P.; Capote, R.; Alvarez-Gomez, J. A.; Berryman, K.; Bejar, M.; Tsige, M.

2009-04-01

In February 2001 a major strike slip earthquake stroke the central part of El Salvador causing hundreds of people killed, thousands injured and extensive damage. After this event the scientific effort was mainly focused on the study of the enormous and catastrophic landslides triggered by this event and no evidences of surface faulting were detected. This earthquake was produced by the reactivation of the Ilopango-San Vicente segment of the El Salvador Fault Zone. Recently, a surface rupture displacement on the ground was identified. The analysis of aerial and field photographs taken few hours after the event and the mapping of the conserved ground structures shows a pure strike-slip displacement ranging from 20 to 50 cm, with secondary features indicating dextral shearing. The paleoseismic analysis made through the excavation of six trenches and Radiocarbon dating indicate a minimum slip rate of 2.0 mm/yr and a recurrence of major ruptures (Mw > 6.5) lower than 500 yr. These evidences give interesting local data to increase our understanding about the tectonic behavior and the way how active deformation develops along the northern limit of the forearc sliver related to the Centroamerican subduction area.
Active tectonics of the Devils Mountain Fault and related structures, northern Puget Lowland and eastern Strait of Juan de Fuca region, Pacific Northwest

USGS Publications Warehouse

Johnson, Samuel Y.; Dadisman, Shawn V.; Mosher, David C.; Blakely, Richard J.; Childs, Jonathan R.

2001-01-01

Information from marine high-resolution and conventional seismic-reflection surveys, aeromagnetic mapping, coastal exposures of Pleistocene strata, and lithologic logs of water wells is used to assess the active tectonics of the northern Puget Lowland and eastern Strait of Juan de Fuca region of the Pacific Northwest. These data indicate that the Devils Mountain Fault and the newly recognized Strawberry Point and Utsalady Point faults are active structures and represent potential earthquake sources.
Characterization of Stream Channel Evolution Due to Extensional Tectonics Along the Western Margin of North Boulder Basin (Bull Mountain), SW Montana with the Use of Geologic Mapping and Thermochronologic (U-Th/He) Dating.

NASA Astrophysics Data System (ADS)

Cataldo, K.; Douglas, B. J.; Yanites, B.

2017-12-01

Landscape response to active tectonics, such as fault motion or regional uplift, can be recorded in river profiles as changes in slope (i.e. knickpoints) or topography. North Boulder basin region (SW Montana), experienced two separate phases of extension, from 45 - 35 Ma and again beginning 14 Ma to the present, producing basin-and-range style fault-blocks. Focusing on the Bull Mountain region, located on the western margin of the North Boulder basin, data is collected to test the hypothesis that Bull Mountain is located on the hanging wall of a half-graben. Our objective is to elucidate the active tectonics of the study area within a regional context by utilizing river profile analysis and thermochronometric data. High-resolution (< 5cm) river profile data is obtained from five of the main tributaries of Bull Mountain. Comprehensive geologic mapping along the main tributaries and topographic highs of the region allowed for the identification and measurement of knickpoints, composition of detailed lithologic descriptions, and analysis of key structural features. The absence of knickpoints within the four tributaries mapped on east Bull Mountain are consistent with a lack of tectonic activity. In contrast, Dearborn Creek, on western Bull Mountain, is located along an active normal fault and presents several knickpoints. Geologic mapping confirms that the primary lithologies of the region belong to the Elkhorn Mountain Volcanics. At lower elevations, there are massive plutonic intrusions of Quartz Monzonite and Diorite, both constituents of the Boulder batholith. These lithologies contain minerals suited for low-temperature thermochronology (U-Th/He) to constrain the timing of tectonic activity (i.e. uplift and exhumation) and erosion rates in the region. High-resolution stream profiles and a 10m DEM are used to delineate watersheds and produce steepness and concavity maps of major tributaries to investigate changes in slope or topography. The effects of extensional
Late-Variscan Tectonic Inheritance and Salt Tectonics Interplay in the Central Lusitanian Basin

NASA Astrophysics Data System (ADS)

Nogueira, Carlos R.; Marques, Fernando O.

2017-04-01

Tectonic inheritance and salt structures can play an important role in the tectono-sedimentary evolution of basins. The Alpine regional stress field in west Iberia had a horizontal maximum compressive stress striking approximately NNW-SSE, related to the Late Miocene inversion event. However, this stress field cannot produce a great deal of the observed and mapped structures in the Lusitanian Basin. Moreover, many observed structures show a trend similar to well-known basement fault systems. The Central Lusitanian basin shows an interesting tectonic structure, the Montejunto structure, generally assigned to this inversion event. Therefore, special attention was paid to: (1) basement control of important observed structures; and (2) diapir tectonics (vertical maximum compressive stress), which can be responsible for significant vertical movements. Based on fieldwork, tectonic analysis and interpretation of geological maps (Portuguese Geological Survey, 1:50000 scale) and geophysical data, our work shows: (1) the Montejunto structure is a composite structure comprising an antiform with a curved hinge and middle Jurassic core, and bounding main faults; (2) the antiform can be divided into three main segments: (i) a northern segment with NNE-SSW trend showing W-dipping bedding bounded at the eastern border by a NNE-SSW striking fault, (ii) a curved central segment, showing the highest topography, with a middle Jurassic core and radial dipping bedding, (iii) a western segment with ENE-WSW trend comprising an antiform with a steeper northern limb and periclinal termination towards WSW, bounded to the south by ENE-WSW reverse faulting, (3) both fold and fault trends at the northern and western segments are parallel to well-known basement faults related to late-Variscan strike-slip systems with NNE-SSW and ENE-WSW trends; (4) given the orientation of Alpine maximum compressive stress, the northern segment border fault should be mostly sinistral strike-slip and the western
Interactions of tectonic, igneous, and hydraulic processes in the North Tharsis Region of Mars

NASA Technical Reports Server (NTRS)

Davis, P. A.; Tanaka, Kenneth L.; Golombek, M. P.; Plescia, J. B.

1991-01-01

Recent work on the north Tharsis of Mars has revealed a complex geologic history involving volcanism, tectonism, flooding, and mass wasting. Our detailed photogeologic analysis of this region found many previously unreported volcanic vents, volcaniclastic flows, irregular cracks, and minor pit chains; additional evidence that volcanic tectonic processes dominated this region throughout Martian geologic time; and the local involvement of these processes with surface and near surface water. Also, photoclinometric profiles were obtained within the region of troughs, simple grabens, and pit chains, as well as average spacings of pits along pit chains. These data were used together with techniques to estimate depths of crustal mechanical discontinuities that may have controlled the development of these features. In turn, such discontinuities may be controlled by stratigraphy, presence of water or ice, or chemical cementation.
The tectonic and volcanic evolution of Venus: Catastrophic or gradual?

NASA Technical Reports Server (NTRS)

Solomon, Sean C.

1993-01-01

Radar imaging and altimetry data from the Magellan mission have yielded important new constraints on the tectonic and volcanic history of Venus and on its internal dynamics. The planet lacks global plate tectonics, but a number of chasm systems and corona moat structures have arcuate planforms, asymmetric topogrpahic profiles, and relief analogous to deep-sea trenches on Earth and may be products of limited lithospheric underthrusting or subduction. Several lines of evidence point to a crust and upper mantle stronger than would be predicted by simple extrapolation from Earth and the 450 K greater surface temperature; these include the unrelaxed depths of impact craters, apparently large values of elastic lithosphere thickness, and large ratios of gravity to topography. The density of impact craters indicates an averate crater retention age of about 500 My, but not more than 5% of the recognized craters have been volcanically embayed. This last observation has led to the proposal that Venus has been subjected to one or more global resurfacing events, the latest about 500 My ago, and that the volcanic flux during intervals between such events has been low. That more recent tectonic activity has been widespread, however, is indicated by the high relief and slopes of mountains, chasm walls, and plateau margins; the significant fraction (0.3) of impact craters deformed by younger faults; and the postformational vertical deformation of long channels. Interior dynamical scenarios advanced to account for episodic volcanic resurfacing include catastrophic overturn of a global lithosphere thickened by cooling or compositional buoyancy and strongly time-dependent mantle convective heat flux. Outgassing considerations and analogy with Earth and other terrestrial planets, however, suggests that such catastrophic models are unlikely. If the mantle of Venus cooled more efficiently than that of Earth because of, say, different boundary conditions, a different flow law, or a
Active Tectonics of Himalayan Faults/Thrusts System in Northern India on the basis of recent & Paleo earthquake Studies

NASA Astrophysics Data System (ADS)

Kumar, S.; Biswal, S.; Parija, M. P.

2016-12-01

The Himalaya overrides the Indian plate along a decollement fault, referred as the Main Himalayan Thrust (MHT). The 2400 km long Himalayan mountain arc in the northern boundary of the Indian sub-continent is one of the most seismically active regions of the world. The Himalayan Frontal Thrust (HFT) is characterized by an abrupt physiographic and tectonic break between the Himalayan front and the Indo-Gangetic plain. The HFT represents the southern surface expression of the MHT on the Himalayan front. The tectonic zone between the Main Boundary Thrust (MBT) and the HFT encompasses the Himalayan Frontal Fault System (HFFS). The zone indicates late Quaternary-Holocene active deformation. Late Quaternary intramontane basin of Dehradun flanked to the south by the Mohand anticline lies between the MBT and the HFT in Garhwal Sub Himalaya. Slip rate 13-15 mm/yr has been estimated on the HFT based on uplifted strath terrace on the Himalyan front (Wesnousky et al. 2006). An out of sequence active fault, Bhauwala Thrust (BT), is observed between the HFT and the MBT. The Himalayan Frontal Fault System includes MBT, BT, HFT and PF active fault structures (Thakur, 2013). The HFFS structures were developed analogous to proto-thrusts in subduction zone, suggesting that the plate boundary is not a single structure, but series of structures across strike. Seismicity recorded by WIHG shows a concentrated belt of seismic events located in the Main Central Thrust Zone and the physiographic transition zone between the Higher and Lesser Himalaya. However, there is quiescence in the Himalayan frontal zone where surface rupture and active faults are reported. GPS measurements indicate the segment between the southern extent of microseismicity zone and the HFT is locked. The great earthquake originating in the locked segment rupture the plate boundary fault and propagate to the Himalaya front and are registered as surface rupture reactivating the fault in the HFFS.
Late Quaternary river channel migrations of the Kura River in Transcaucasia - tectonic versus climatic causes

NASA Astrophysics Data System (ADS)

von Suchodoletz, Hans; Gärtner, Andreas; Hoth, Silvan; Umlauft, Josefine; Godoladze, Tea; Faust, Dominik

2015-04-01

Large-scale river channel migrations either in the form of avulsions or combing, i.e. progressive lateral migrations, are global phenomena during the Late Quaternary. Such channel migrations were triggered by tectonics, climate change, human activity or a combination of those factors. River channel migrations have the potential to cause significant human and economic losses. Thus, a more thorough knowledge about underlying causes and process rates is essential. Furthermore, such studies will elucidate the sensitivity or robustness of rivers to different external and internal forcing-agents, i.e. they help to identify the dominant drivers of regional landscape evolution. The Caucasus region is part of the active collision zone between the Africa-Arabian and the Eurasian plates, and is characterized by high current tectonic activity. Furthermore, significant environmental changes took place during the Late Quaternary, i.e. the shrinking or even disappearance of glaciers in the Greater and Lesser Caucasus or fundamental changes of the vegetation cover varying between woodland and grassland-dominated vegetation. The Kura River is the main gaining stream of the Transcaucasian Depression located between the Greater Caucasus Mountains in the north and the Lesser Caucasus Mountains in the south, and receives several tributaries from both mountain ranges. This study focusses on the middle course of the Kura River in eastern Georgia, SE of the city of Tbilisi. Integration of fluvial geomorphology, geochronology, heavy mineral analyses and seismo-tectonic analyses demonstrates that this part of the Kura River underwent large-scale channel migrations up to >10 km during Late Pleistocene and Holocene. It is interpreted that these movements followed both tectonic and climatic triggers: Whereas SW-ward migrations were caused by tectonic uplift in and SW-directed advance of the Kura fold and thrust belt as part of the Greater Caucasus, NE-ward migrations occurred during cold
Asymmetric bagging and feature selection for activities prediction of drug molecules.

PubMed

Li, Guo-Zheng; Meng, Hao-Hua; Lu, Wen-Cong; Yang, Jack Y; Yang, Mary Qu

2008-05-28

Activities of drug molecules can be predicted by QSAR (quantitative structure activity relationship) models, which overcomes the disadvantages of high cost and long cycle by employing the traditional experimental method. With the fact that the number of drug molecules with positive activity is rather fewer than that of negatives, it is important to predict molecular activities considering such an unbalanced situation. Here, asymmetric bagging and feature selection are introduced into the problem and asymmetric bagging of support vector machines (asBagging) is proposed on predicting drug activities to treat the unbalanced problem. At the same time, the features extracted from the structures of drug molecules affect prediction accuracy of QSAR models. Therefore, a novel algorithm named PRIFEAB is proposed, which applies an embedded feature selection method to remove redundant and irrelevant features for asBagging. Numerical experimental results on a data set of molecular activities show that asBagging improve the AUC and sensitivity values of molecular activities and PRIFEAB with feature selection further helps to improve the prediction ability. Asymmetric bagging can help to improve prediction accuracy of activities of drug molecules, which can be furthermore improved by performing feature selection to select relevant features from the drug molecules data sets.
Seafloor Tectonic Fabric from Satellite Altimetry

NASA Astrophysics Data System (ADS)

Smith, Walter H. F.

Ocean floor structures with horizontal scales of 10 to a few hundred kilometers and vertical scales of 100 m or more generate sea surface gravity anomalies observable with satellite altimetry. Prior to 1990, altimeter data resolved only tectonic lineaments, some seamounts, and some aspects of mid-ocean ridge structure. New altimeter data available since mid-1995 resolve 10-km--scale structures over nearly all the world's oceans. These data are the basis of new global bathymetric maps and have been interpreted as exhibiting complexities in the sea floor spreading process including ridge jumps, propagating rifts, and variations in magma supply. This chapter reviews the satellite altimetry technique and its resolution of tectonic structures, gives examples of intriguing tectonic phenomena, and shows that structures as small as abyssal hills are partially resolved. A new result obtained here is that the amplitude of the fine-scale (10--80 km) roughness of old ocean floor is spreading-rate dependent in the same that it is at mid-ocean ridges, suggesting that fine-scale tectonic fabric is generated nearly exclusively by ridge-axis processes.
The tectonic evolution of the Irtysh tectonic belt: New zircon U-Pb ages of arc-related and collisional granitoids in the Kalaxiangar tectonic belt, NW China

NASA Astrophysics Data System (ADS)

Hong, Tao; Klemd, Reiner; Gao, Jun; Xiang, Peng; Xu, Xing-Wang; You, Jun; Wang, Xin-Shui; Wu, Chu; Li, Hao; Ke, Qiang

2017-02-01

Precise geochronological constraints of the Irtysh tectonic belt situated between the Saur Island Arc and the Altay Terrane are crucial to a better understanding of the tectonic evolution of the Central Asian Orogenic Belt (CAOB). Recently, we discovered repeatedly deformed arc-related and collisional granitoids in the Kalaxiangar tectonic belt (KTB), which is located in the eastern part of the Irtysh tectonic belt. In this study, we report new whole-rock geochemical, zircon U-Pb and Hf isotopic data of the arc-related and collisional granitoids. Our data reveal that 1) arc-related granodioritic porphyries formed at ca. 382-374 Ma. Recrystallized zircon grains from a (ultra-)mylonitic granodiorite of the Laoshankou zone in the southern KTB display a U-Pb age of ca. 360 Ma; 2) syn-collisional granodioritic porphyries, which distribute along faults and parallel to the cleavage, were emplaced at ca. 367-356 Ma, with εHf(t) values varying from + 7.8 to + 14.2 and Hf model ages from 873 to 459 Ma; 3) a post-collisional A-type granodioritic porphyry, which crosscuts the NW-NNW trending schistosity of the metasedimentary country rocks at a low angle, has an age of ca. 324-320 Ma, while the εHf(t) values range from + 7.6 to + 14.4 with Hf model ages from 850 to 416 Ma; 4) post-collisional strike-slip A-type granite dykes, exposed along strike-slip faults, gave ages between 287 and 279 Ma, whereas the εHf(t) values range from + 4.9 to + 12.7 and the Hf model ages from 995 to 500 Ma; and 5) A-type biotite granite dykes, which intruded along conjugate tension joints, have ages of 274-271 Ma, and εHf(t) values from + 1.5 to + 13.2 with Hf model ages from 1196 to 454 Ma. Consequently, we propose that the collision between the Saur Island Arc and the Altay Terrane occurred in the Early Carboniferous (ca. 367-356 Ma) and the subsequent post-collisional tectonic process continued to the Late Carboniferous (ca. 324-320 Ma). It is further suggested that the Irtysh tectonic belt
Barrel organ of plate tectonics - a new tool for outreach and education

NASA Astrophysics Data System (ADS)

Broz, Petr; Machek, Matěj; Šorm, Zdar

2016-04-01

Plate tectonics is the major geological concept to explain dynamics and structure of Earth's outer shell, the lithosphere. In the plate tectonic theory processes in the Earth lithosphere and its dynamics is driven by the relative motion and interaction of lithospheric plates. Geologically most active regions on Earth often correlate with the lithospheric plate boundaries. Thus for explaining the earth surface evolution, mountain building, volcanism and earthquake origin it is important to understand processes at the plate boundaries. However these processes associated with plate tectonics usually require significant period of time to take effects, therefore, their entire cycles cannot be directly observed in the nature by humans. This makes a challenge for scientists studying these processes, but also for teachers and popularizers trying to explain them to students and to the general public. Therefore, to overcome this problem, we developed a mechanical model of plate tectonics enabling demonstration of most important processes associated with plate tectonics in real time. The mechanical model is a wooden box, more specifically a special type of barrel organ, with hand painted backdrops in the front side. These backdrops are divided into several components representing geodynamic processes associated with plate tectonics, specifically convective currents occurring in the mantle, sea-floor spreading, a subduction of the oceanic crust under the continental crust, partial melting and volcanism associated with subduction, a formation of magmatic stripes, an ascent of mantle plume throughout the mantle, a volcanic activity associated with hot spots, and a formation and degradation of volcanic islands on moving lithospheric plate. All components are set in motion by a handle controlled by a human operator, and the scene is illuminated with colored lights controlled automatically by an electric device embedded in the box. Operation of the model may be seen on www
Features on Venus generated by plate boundary processes

NASA Technical Reports Server (NTRS)

Mckenzie, Dan; Ford, Peter G.; Johnson, Catherine; Parsons, Barry; Sandwell, David; Saunders, Stephen; Solomon, Sean C.

1992-01-01

Various observations suggest that there are processes on Venus that produce features similar to those associated with plate boundaries on earth. Synthetic aperture radar images of Venus, taken with a radar whose wavelength is 12.6 cm, are compared with GLORIA images of active plate boundaries, obtained with a sound source whose wavelength is 23 cm. Features similar to transform faults and to abyssal hills on slow and fast spreading ridges can be recognized within the Artemis region of Venus but are not clearly visible elsewhere. The composition of the basalts measured by the Venera 13 and 14 and the Vega 2 spacecraft corresponds to that expected from adiabatic decompression, like that which occurs beneath spreading ridges on earth. Structures that resemble trenches are widespread on Venus and show the same curvature and asymmetry as they do on earth. These observations suggest that the same simple geophysical models that have been so successfully used to understand the tectonics of earth can also be applied to Venus.
Active tectonic deformation of the western Indian plate boundary: A case study from the Chaman Fault System

NASA Astrophysics Data System (ADS)

Crupa, Wanda E.; Khan, Shuhab D.; Huang, Jingqiu; Khan, Abdul S.; Kasi, Aimal

2017-10-01

Collision of the Eurasian and Indian plates has resulted in two spatially offset subduction zones, the Makran subduction zone to the south and the Himalayan convergent margin to the north. These zones are linked by a system of left-lateral strike-slip faults known as the Chaman Fault System, ∼1200 km, which spans along western Pakistan. Although this is one of the greatest strike-slip faults, yet temporal and spatial variation in displacement has not been adequately defined along this fault system. This study conducted geomorphic and geodetic investigations along the Chaman Fault in a search for evidence of spatial variations in motion. Four study areas were selected over the span of the Chaman Fault: (1) Tarnak-Rud area over the Tarnak-Rud valley, (2) Spinatizha area over the Spinatizha Mountain Range, (3) Nushki area over the Nushki basin, and (4) Kharan area over the northern tip of the Central Makran Mountains. Remote sensing data allowed for in depth mapping of different components and faults within the Kohjak group. Wind and water gap pairs along with offset rivers were identified using high-resolution imagery and digital-elevation models to show displacement for the four study areas. The mountain-front-sinuosity ratio, valley height-to-width-ratio, and the stream-length-gradient index were calculated and used to determine the relative tectonic activity of each area. These geomorphic indices suggest that the Kharan area is the most active and the Tarnak-Rud area is the least active. GPS data were processed into a stable Indian plate reference frame and analyzed. Fault parallel velocity versus fault normal distance yielded a ∼8-10 mm/yr displacement rate along the Chaman Fault just north of the Spinatizha area. InSAR data were also integrated to assess displacement rates along the fault system. Geodetic data support that ultra-slow earthquakes similar to those that strike along other major strike-slip faults, such as the San Andreas Fault System, are
Planetary Geophysics and Tectonics

NASA Technical Reports Server (NTRS)

Parmentier, E. M.

1997-01-01

Research supported by grant NAGW-1928 has addressed a variety of problems related to planetary evolution. One important focus has been on questions related to the role of chemical buoyancy in planetary evolution with application to both Venus and the Moon. We have developed a model for the evolution of the Moon (Hess and Parmentier, 1995) in which dense, highly radioactive, late stage magma ocean cumulates sink forming a core. This core heats the overlying, chemically layered mantle giving rise to a heated, chemically well-mixed layer that thickens with time. This Mixed layer eventually becomes hot enough and thick enough that its top begins to melt at a pressure low enough that melt is buoyant, thus creating mare basalts from a high pressure source of the correct composition and at an appropriate time in lunar evolution. In work completed during the last year, numerical experiments on convection in a chemically stably stratified fluid layer heated from below have been completed. These results show us how to calculate the evolution of a mixed layer in the Moon, depending on the heat production in the ilmenite- cumulate core and the chemical stratification of the overlying mantle. Chemical stratification of the mantle after its initial differentiation is would trap heat in the deep interior and prevent the rapid rise of plumes with accompanying volcanism. This trapping of heat in the interior can explain the thickness of the lunar lithosphere as a function of time as well as the magmatic evolution. We show that heat transported to the base of the lithosphere at a rate determined by current estimates of radioactivity in the Moon would not satisfy constraints on elastic lithosphere thickness from tectonic feature associated with basin loading. Trapping heat at depth by a chemically stratified mantle may also explain the absence of global compressional features on the surface that previous models predict for an initially hot lunar interior. For Venus, we developed a

Polyphase thrust tectonic in the Barberton greenstone belt

NASA Technical Reports Server (NTRS)

Paris, I. A.

1986-01-01

In the circa 3.5 by-old Barberton greenstone belt, the supracrustal rocks form a thick and strongly deformed thrust complex. Structural studies in the southern part of the belt have shown that 2 separate phases of over-thrusting (D sub 1 and D sub 2) successively dismembered the original stratigraphy. Thrust nappes were subsequently refolded during later deformations (D sub 3 and D sub 4). This report deals with the second thrusting event which, in the study region appears to be dominant, and (unlike the earlier thrusting), affects the entire supracrustal pile. The supracrustal rocks form a predominantly NE/SW oriented, SE dipping tectonic fan (the D sub 2 fan) in which tectonic slices of ophiolitic-like rocks are interleaved with younger sedimentary sequences of the Diepgezet and malalotcha groups. Structural and sedimentological data indicate that the D sub 2 tectonic fan was formed during a prolonged, multi-stage regional horizontal shortening event during which several types of internal deformation mechanisms were successively and/or simultaneously active. Movement appears to have been predominantly to the NW and to the N. During D sub 2, periods of quiescence and sedimentation followed periods of thrust propagation. Although the exact kinematics which led to the formation of this fan is not yet known, paleoenvironmental interpretations together with structural data suggest that D sub 2 was probably related to (an) Archean collision(s).
Surface-wave potential for triggering tectonic (nonvolcanic) tremor

USGS Publications Warehouse

Hill, D.P.

2010-01-01

Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle is anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45?? incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia mega-thrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction, ????? 0.2). However, documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, is associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (?? ~ 0.6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.
Tectonic influences on the preservation of marine terraces: Old and new evidence from Santa Catalina Island, California

USGS Publications Warehouse

Schumann, R. Randall; Minor, Scott A.; Muhs, Daniel R.; Groves, Lindsey T.; McGeehin, John P.

2012-01-01

The California Channel Islands contain some of the best geologic records of past climate and sea-level changes, recorded in uplifted, fossil-bearing marine terrace deposits. Among the eight California Channel Islands and the nearby Palos Verdes Hills, only Santa Catalina Island does not exhibit prominent emergent marine terraces, though the same terrace-forming processes that acted on the other Channel Islands must also have occurred on Santa Catalina. We re-evaluated previous researchers' field evidence and examined new topographic, bathymetric, and stream-profile data in order to find possible explanations for the lack of obvious marine terrace landforms or deposits on the island today. The most likely explanation is associated with the island's unresolved tectonic history, with evidence for both recent uplift and subsidence being offered by different researchers. Bathymetric and seismic reflection data indicate the presence of submerged terrace-like landforms from a few meters below present sea level to depths far exceeding that of the lowest glacial lowstand, suggesting that the Catalina Island block may have subsided, submerging marine terraces that would have formed in the late Quaternary. Similar submerged marine terrace landforms exist offshore of all of the other California Channel Islands, including some at anomalously great depths, but late Quaternary uplift is well documented on those islands. Therefore, such submarine features must be more thoroughly investigated and adequately explained before they can be accepted as definitive evidence of subsidence. Nevertheless, the striking similarity of the terrace-like features around Santa Catalina Island to those surrounding the other, uplifting, Channel Islands prompted us to investigate other lines of evidence of tectonic activity, such as stream profile data. Recent uplift is suggested by disequilibrium stream profiles on the western side of the island, including nickpoints and profile convexities. Rapid
The alternative concept of global tectonics

NASA Astrophysics Data System (ADS)

Anokhin, Vladimir; Kholmyansky, Mikhael

2016-04-01

The existing plate tectonic paradigm becomes more questionable in relation to the new facts of the Earth. The most complete to date criticism of plate tectonics provisions contained in the article (Pratt, 2000). Authors can recall a few facts that contradict the idea of long-range movement of plates: - The absence of convection cells in the mantle, detected by seismic tomography; - The presence of long-lived deep regmatic network in the crust, not distorted by the movement of plates; - The inability of linking the global geometry of the of mutual long-distance movement of plates. All this gives reason to believe that correct, or at least a satisfactory concept of global tectonics are not exist now. After overcoming the usual inertia of thinking the plate paradigm in the foreseeable future will replace by different concept, more relevant as the observable facts of the Earth and the well-known physical laws. The authors suggest that currently accumulated sufficient volume of facts and theoretical ideas for the synthesis of a new general hypothesis of the structure and dynamics of the Earth. Analysis of the existing tectonic theory suggests that most of their provisions are mutually compatible. Obviously, plume tectonics perfectly compatible with any of classical models. It contradicts the only plate tectonics (movement of hot spots in principle not linked either with each other or with the general picture of the plate movements, the presence of mantle convection and mantle streams are mutually exclusive, and so on). The probable transfer of the heated material down up within the Earth may occur in various forms, the simplest of which (and, consequently, the most probable) are presented plumes. The existence in the mantle numerous large volumes of decompressed substances (detected seismic tomography), can be correlated with the bodies of plumes at different stages of uplift. Plumes who raise to the bottom of the lithosphere, to spread out to the sides and form a set
Tectonic and magmatic controls on hydrothermal activity in the Woodlark Basin

NASA Astrophysics Data System (ADS)

Laurila, T. E.; Petersen, S.; Devey, C. W.; Baker, E. T.; Augustin, N.; Hannington, M. D.

2012-09-01

The Woodlark Basin is one of the rare places on earth where the transition from continental breakup to seafloor spreading can be observed. The potential juxtaposition of continental rocks, a large magmatic heat source, crustal-scale faulting, and hydrothermal circulation has made the Woodlark Basin a prime target for seafloor mineral exploration. However, over the past 20 years, only two locations of active hydrothermalism had been found. In 2009 we surveyed 435 km of the spreading axis for the presence of hydrothermal plumes. Only one additional plume was found, bringing the total number of plumes known over 520 km of ridge axis to only 3, much less than at ridges with similar spreading rates globally. Particularly the western half of the basin (280 km of axis) is apparently devoid of high temperature plumes despite having thick crust and a presumably high magmatic budget. This paucity of hydrothermal activity may be related to the peculiar tectonic setting at Woodlark, where repeated ridge jumps and a re-location of the rotation pole both lead to axial magmatism being more widely distributed than at many other, more mature and stable mid-ocean ridges. These factors could inhibit the development of both a stable magmatic heat source and the deeply penetrating faults needed to create long-lived hydrothermal systems. We conclude that large seafloor massive sulfide deposits, potential targets for seafloor mineral exploration, will probably not be present along the spreading axis of the Woodlark Basin, especially in its younger, western portion.
Discordant Early Miocene palaeomagnetic directions at the vicinity of the North Aegean Trough: tectonic or palaeofield feature?

NASA Astrophysics Data System (ADS)

Kontopoulou, D.; Valet, J. P.; Zananiri, I.; Voidomatis, P.

2017-12-01

The North Aegean Trough (N.A.T) is a major tectonic feature of North Aegean Sea. This is a large NE-SW transcurrent lineament that is interpreted as the continuation of the North Anatolian Fault, with a prominent dextral strike-slip motion. IAn intense igneous activity has developed along the N.A.T to its north through the presence of abundant plutonism and volcanism from Early Oligocene to Pliocene. A considerable amount of palaeomagnetic data display a systematic pattern of clockwise rotations with angles varying between 20°-40° since the Early Oligocene. In order to document the impact of the N.A.T to regional rotations, early Miocene lava flows have been extensively sampled in the islands of Samothrace and Lemnos located to the north and south of N.A.T, respectively. Two sets of directions have been defined from the palaeomagnetic studies. The first one corresponds to the expected North-East declinations with positive inclinations or to reversed South-West declinations with negative inclinations that were previously interpreted as a dextral rotations of this area. The second set, exhibits discordant and apparently erratic directions despite quite acceptable demagnetization behaviour and magnetic characteristics. In order to constrain further these directions we performed new samplings. The new measurements which include Thellier absolute palaeointensity experiments reveal that the intermediate directions are associated with low field values for Samothrace with a transitional field recorded between 21 and 17 Ma. The presence of single magnetization component and the variability of the lavas do not favor the possibility of self-reversal mechanisms. The consistency of the directions within each flow but also between lava flows of comparable ages in the two islands and the presence of normal and reverse polarities point to records of transitional directions. In both islands, the intermediate virtual geomagnetic poles exhibit a preference for equatorial latitudes
Active Tectonics Around Pisagua, Northern Chile Gap: Seismological and Neotectonic Approaches

NASA Astrophysics Data System (ADS)

Comte, D.; Carrizo, D.; Peyrat, S.

2013-12-01

Northern Chile is a recognized mature seismic gap that is reaching the end of its megathrust cycle. Deformation associated with the convergence between the Nazca and the South American Plates is mainly absorbed along the interplate contact, but also partially accommodated along the upper plate. Even though distribution of the active deformation along this plate has been documented mainly in the backarc region, Late Cenozoic structures have been recognized along the forearc suggesting that some part of this deformation is also accommodated along the coastal region. Recent paleoseismological studies suggest that some of these structures are tectonically active and some could be potentially active, capable to generate shallow intraplate earthquakes (Mw˜7). However, seismological and geodetical evidences of the fault activation mechanisms are poorly documented, and the activation process remain not elucidate. Currently, Northern Chile seismic gap is monitored by regional seismic networks and partially studied by temporary local seismological experiments. Results of these studies suggest the presence of shallow seismicity along the forearc, but the relationships between upper plate faults and the seismicity has not been yet explored. We perform a detailed seismotectonic analysis of the subduction-forearc system in the central part of the Northern Chile seismic gap to establish relationships between the plate contact deformation and the upper plate faults. We present preliminary results of data recorded by a dense seismic network (three components continuous recording) deployed around Pisagua, between the coastline and the Central Depression, during several months. Pisagua region was chosen because the forearc faults exhibit an extraordinary well-preserved morphotectonic expression, and the upper part of the seismogenic interplate contact shows abundant continental intraplate seismicity that could be associated with the faults systems. The data recorded in this area
Peculiar Active-Tectonic Landscape Within the Sanctuary of Zeus at Mt. Lykaion (Peloponnese, Greece)

NASA Astrophysics Data System (ADS)

Davis, G. H.

2008-12-01

The Sanctuary of Zeus (Mt. Lykaion) lies in the Peloponnese within the Pindos fold and thrust belt. It is the object of investigation of the Mt. Lykaion Excavation and Survey (http://lykaionexcavation.org/). Mt. Lykaion is a thrust klippe, on the summit of which is an upper sanctuary marked by an ash altar, temenos, and column bases. Earliest objects recovered from the ash altar go back to 3000 BCE, leading Dr. David Romano (University of Pennsylvania), a principal leader of the project, to conclude that worship of divinities on the summit is ancient. Detailed structural geological mapping reveals one dimension of the "power" of the site. Crisscrossing the upper sanctuary are scree bands that mark the traces of active normal faults, which are expressions of tectonic stretching of the Aegean region. The scree bands, composed of cinder-block-sized limestone blocks, range up to 10 m in outcrop breadth, 100 m in length, and 5 m in thickness. Though discontinuous, most of the scree bands lie precisely on the traces of through-going faults, which cut and displace the sedimentary formations of the Pindos group. Some cut the thrust fault, whose elliptical trace defines the Lykaion klippe. What makes the scree bands of this active-tectonic landscape "peculiar" is that there are no cliffs from which the scree descends. Rather, the bands of scree occur along flanks of smooth, rounded hillslopes and ridges. The scree bands coincide with modest steps in the topography, ranging from tens of centimeters to several tens of meters. The specific bedrock formation where the bands are best developed is an Upper Cretaceous limestone whose average platy-bedding thickness (approximately 20 cm) matches closely the average joint spacing. The limestone has little mechanical integrity. It cannot support itself as a scarp footwall and instead collapses into a pile of scree, whose upper-surface inclination conforms to a stable angle of repose. Evidence of the contemporary nature of this
3D upper crustal seismic structure across Santorini volcanic field: Constraints on magmatic and tectonic interactions

NASA Astrophysics Data System (ADS)

Heath, B.; Hooft, E. E. E.; Toomey, D. R.; Papazachos, C. V.; Walls, K.; Paulatto, M.; Morgan, J. V.; Nomikou, P.; Warner, M.

2017-12-01

To investigate magmatic-tectonic interactions at an arc volcano, we collected a dense, active-source, seismic dataset across the Santorini Volcano, Greece, with 90 ocean bottom seismometers, 65 land seismometers, and 14,300 marine sound sources. We use over 140,000 travel-time picks to obtain a P-wave tomography model of the upper crustal structure of the Santorini volcano and surrounding tectonically extended region. Regionally, the shallow (<2 km) velocity structure is dominated by low- and high-velocity anomalies of several sediment-filled grabens and horsts of Attico-Cycladic metamorphic basement, which correlate well with Bouguer gravity anomalies and preliminary shallow attenuation results (using waveform amplitudes and t* values). We find regional Pliocene and younger faults bounding basement grabens and horsts to be predominately oriented in a NE-SW direction with Santorini itself located in a graben bounded by faults striking in this direction. In contrast, volcanic vents and dikes expressed at the surface seem to strike about 20° clockwise relative to these regional faults. In the northern caldera of Santorini, a 4-km wide region of anomalously low velocities and high attenuation directly overlies an inferred source of 2011-2012 inflation (4-4.5 km depth), however it is located at shallower depths ( 1-2km). The imaged low-velocity anomaly may correspond to hydrothermal activity (due to increased porosity and alteration) and/or brecciation from a prior episode of caldera collapse. It is bounded by anomalously fast velocities (at 1-2 km depth) that parallel the regional fault orientation and are correspondingly rotated 20° to surface dikes. At 4-5 km depth beneath the northern caldera basin, low-velocity anomalies and attenuated seismic arrivals provide preliminary evidence for a magma body; the low-velocity anomaly is elongated in the same direction as regional volcanic vents. The difference in strike of volcanic and tectonic features indicates oblique
Ganges-Brahmaputra Delta: Balance of Subsidence, Sea level and Sedimentation in a Tectonically-Active Delta (Invited)

NASA Astrophysics Data System (ADS)

Steckler, M. S.; Goodbred, S. L.; Akhter, S. H.; Seeber, L.; Reitz, M. D.; Paola, C.; Nooner, S. L.; DeWolf, S.; Ferguson, E. K.; Gale, J.; Hossain, S.; Howe, M.; Kim, W.; McHugh, C. M.; Mondal, D. R.; Petter, A. L.; Pickering, J.; Sincavage, R.; Williams, L. A.; Wilson, C.; Zumberge, M. A.

2013-12-01

Bangladesh is vulnerable to a host of short and long-term natural hazards - widespread seasonal flooding, river erosion and channel avulsions, permanent land loss from sea level rise, natural groundwater arsenic, recurrent cyclones, landslides and huge earthquakes. These hazards derive from active fluvial processes related to the growth of the delta and the tectonics at the India-Burma-Tibet plate junctions. The Ganges and Brahmaputra rivers drain 3/4 of the Himalayas and carry ~1 GT/y of sediment, 6-8% of the total world flux. In Bangladesh, these two great rivers combine with the Meghna River to form the Ganges-Brahmaputra-Meghna Delta (GBMD). The seasonality of the rivers' water and sediment discharge is a major influence causing widespread flooding during the summer monsoon. The mass of the water is so great that it causes 5-6 cm of seasonal elastic deformation of the delta discerned by our GPS data. Over the longer-term, the rivers are also dynamic. Two centuries ago, the Brahmaputra River avulsed westward up to 100 km and has since captured other rivers. The primary mouth of the Ganges has shifted 100s of km eastward from the Hooghly River over the last 400y, finally joining the Brahmaputra in the 19th century. These avulsions are influenced by the tectonics of the delta. On the east side of Bangladesh, the >16 km thick GBMD is being overridden by the Burma Arc where the attempted subduction of such a thick sediment pile has created a huge accretionary prism. The foldbelt is up to 250-km wide and its front is buried beneath the delta. The main Himalayan thrust front is <100 km north, but adjacent to the GBMD is the Shillong Massif, a 300-km long, 2-km high block of uplifted Indian basement that is overthrusting and depressing GBMD sediments to the south. The overthrusting Shillong Massif may represent a forward jump of the Himalayan front to a new plate boundary. This area ruptured in a ~M8 1897 earthquake. Subsidence from the tectonics and differential
Late Pleistocene and Holocene uplift history of Cyprus: implications for active tectonics along the southern margin of the Anatolian microplate

USGS Publications Warehouse

Harrison, R.W.; Tsiolakis, E.; Stone, B.D.; Lord, A.; McGeehin, J.P.; Mahan, S.A.; Chirico, P.

2013-01-01

The nature of the southern margin of the Anatolian microplate during the Neogene is complex, controversial and fundamental in understanding active plate-margin tectonics and natural hazards in the Eastern Mediterranean region. Our investigation provides new insights into the Late Pleistocene uplift history of Cyprus and the Troodos Ophiolite. We provide isotopic (14C) and radiogenic (luminescence) dates of outcropping marine sediments in eastern Cyprus that identify periods of deposition during marine isotope stages (MIS) 3, 4, 5 and 6. Past sea-levels indicated by these deposits are c. 95±25 m higher in elevation than estimates of worldwide eustatic sea-level. An uplift rate of c. 1.8 mm/year and possibly as much as c. 4.1 mm/year in the past c. 26–40 ka is indicated. Holocene marine deposits also occur at elevations higher than those expected for past SL and suggest uplift rates of c. 1.2–2.1 mm/year. MIS-3 marine deposits that crop out in southern and western Cyprus indicate uniform island-wide uplift. We propose a model of tectonic wedging at a plate-bounding restraining bend as a mechanism for Late Pleistocene to Holocene uplift of Cyprus; uplift is accommodated by deformation and seismicity along the margins of the Troodos Ophiolite and re-activation of its low-angle, basal shear zone.
Associations between park features and adolescent park use for physical activity.

PubMed

Edwards, Nicole; Hooper, Paula; Knuiman, Matthew; Foster, Sarah; Giles-Corti, Billie

2015-02-18

Eighty per cent of adolescents globally do insufficient physical activity. Parks are a popular place for adolescents to be active. However, little is known about which park features are associated with higher levels of park use by adolescents. This study aimed to examine which environmental park features, and combination of features, were correlated with higher levels of park use for physical activity among adolescents. By examining park features in parks used by adolescents for physical activity, this study also aimed to create a park 'attractiveness' score predictive of adolescent park use, and to identify factors that might predict use of their closest park. Adolescents (n = 1304) living in Geraldton, a large rural centre of Western Australia, completed a survey that measured physical activity behaviour, perceptions of park availability and the main park used for physical activity. All parks in the study area (n = 58) were digitized using a Geographic Information System (GIS) and features audited using the Public Open Space Desktop Auditing Tool (POSDAT). Only 27% of participants reported using their closest park for physical activity. Park use was associated with seven features: presence of a skate park, walking paths, barbeques, picnic table, public access toilets, lighting around courts and equipment and number of trees >25. When combined to create an overall attractiveness score, every additional 'attractive' feature present, resulted in a park being nearly three times more likely to be in the high use category. To increase park use for physical activity, urban planners and designers should incorporate park features attractive to adolescents.
Fault kinematics and active tectonics of the Sabah margin: Insights from the 2015, Mw 6.0, Mt. Kinabalu earthquake

NASA Astrophysics Data System (ADS)

Wang, Y.; Wei, S.; Tapponnier, P.; WANG, X.; Lindsey, E.; Sieh, K.

2016-12-01

A gravity-driven "Mega-Landslide" model has been evoked to explain the shortening seen offshore Sabah and Brunei in oil-company seismic data. Although this model is considered to account simultaneously for recent folding at the edge of the submarine NW Sabah trough and normal faulting on the Sabah shelf, such a gravity-driven model is not consistent with geodetic data or critical examination of extant structural restorations. The rupture that produced the 2015 Mw6.0 Mt. Kinabalu earthquake is also inconsistent with the gravity-driven model. Our teleseismic analysis shows that the centroid depth of that earthquake's mainshock was 13 to 14 km, and its favored fault-plane solution is a 60° NW-dipping normal fault. Our finite-rupture model exhibits major fault slip between 5 and 15 km depth, in keeping with our InSAR analysis, which shows no appreciable surface deformation. Both the hypocentral depth and the depth of principal slip are far too deep to be explained by gravity-driven failure, as such a model would predict a listric normal fault connecting at a much shallower depth with a very gentle detachment. Our regional mapping of tectonic landforms also suggests the recent rupture is part of a 200-km long system of narrowly distributed active extension in northern Sabah. Taken together, the nature of the 2015 rupture, the belt of active normal faults, and structural consideration indicate that active tectonic shortening plays the leading role in controlling the overall deformation of northern Sabah and that deep-seated, onland normal faulting likely results from an abrupt change in the dip-angle of the collision interface beneath the Sabah accretionary prism.
Probabilistic estimation of long-term volcanic hazard under evolving tectonic conditions in a 1 Ma timeframe

NASA Astrophysics Data System (ADS)

Jaquet, O.; Lantuéjoul, C.; Goto, J.

2017-10-01

Risk assessments in relation to the siting of potential deep geological repositories for radioactive wastes demand the estimation of long-term tectonic hazards such as volcanicity and rock deformation. Owing to their tectonic situation, such evaluations concern many industrial regions around the world. For sites near volcanically active regions, a prevailing source of uncertainty is related to volcanic hazard. For specific situations, in particular in relation to geological repository siting, the requirements for the assessment of volcanic and tectonic hazards have to be expanded to 1 million years. At such time scales, tectonic changes are likely to influence volcanic hazard and therefore a particular stochastic model needs to be developed for the estimation of volcanic hazard. The concepts and theoretical basis of the proposed model are given and a methodological illustration is provided using data from the Tohoku region of Japan.
Seismic evidence for change of the tectonic regime in Messinian, northern Marmara Sea, Turkey

NASA Astrophysics Data System (ADS)

Alp, Hakan; Vardar, Denizhan; Alpar, Bedri; Ustaömer, Timur

2018-01-01

New Chirp seismic data collected from the northern margin of the Marmara Sea in June 2015 and previous Sparker seismic profiles recorded in 1999 suggest a change in tectonic regime in Messinian. New tectonic lineaments and fault segments were detected at offshore the Çekmece lagoons region that is located on one of the possible water corridors with the Paratethys. The faults only affect the older seismic unit (U1), which can be best outlined on the Chirp data. The E-W trending fault offshore Avcılar (OAF) borders the northern edge of a tightly folded sedimentary zone. The NNE-SSW trending fault, namely the Büyükçekmece Fault (BF), passing through the Büyükçekmece Bay, follows a buried valley. Its evolution must be related to the development of the Early Miocene - Early Pliocene Thrace-Eskişehir fault zone (TEFZ). BF and OAF indicate old tectonic activities in the region, which continued to the North Anatolian fault becoming the most dominant tectonic element in the region. The upper surface of the stratigraphic unit U1 and its terraces define the thickness of younger deposits (U2), which is thinner in the middle of the shelf. The morphology of the tightly folded zone controls those terraces, which correspond to the Bakırköy Formation and Kıraç member on land. The topmost parts of the terraces must have been eroded during sea level low-stands and cutting of the paleo-valleys. There is no evidence of any tectonic deformation or active fault in the younger seismic unit (U2).
Collisional Tectonics in the St. Elias Orogen, Alaska Observed by GPS

NASA Astrophysics Data System (ADS)

Elliott, J.; Freymueller, J. T.; Larsen, C. F.

2008-12-01

The rugged topography of the St. Elias orogen of southern Alaska and the adjacent region of Canada is the result of the on-going collision of the Yakutat block with southern Alaska. Nearly 45 mm/yr of NW-SE directed convergence from the collision is currently accommodated within the St. Elias orogen. A key to understanding this complex collisional boundary is knowing the locations of the structures taking up the convergence. GPS provides a snapshot of the present-day strain field and helps to delineate active structures. As part of the St. Elias Erosion/Tectonics Project (STEEP), we re-surveyed 70 campaign GPS sites across the St. Elias orogen during the summer of 2008. Strain rates derived from our GPS data highlight several areas within the St. Elias orogen. The highest strain rates occur across Icy Bay and the western edge of the Malaspina Glacier. Rates there approach -1 microstrain/yr, a value higher than that observed in the Himalaya. Lower, but still significant, strain rates of about -0.2 microstrain/yr extend north from Icy Bay to the region surrounding Mt. St. Elias. The second major focus of compressive strain in the orogen is centered over the Yakataga fold-and-thrust belt. Strain rates there are in the range of -0.40 to -0.50 microstrain/yr. Little significant strain is seen across the Bagley icefield or to the north of that feature. These results suggest that most of the convergence across the St. Elias orogen is currently accommodated on structures located south of the Bagely icefield, specifically in the Icy Bay, upper Malaspina/Mt. St. Elias, and Yakataga fold-and-thrust belt regions. We use block modeling techniques to describe the tectonic elements of the St. Elias orogen and connect them with the tectonic regime in southeast Alaska. Our preliminary results indicate that a single thrust fault through Icy Bay cannot explain the data there; multiple NW and N directed thrust faults through Icy Bay, along the western edge of the Malaspina Glacier
The interior of Venus and Tectonic implications

NASA Technical Reports Server (NTRS)

Phillips, R. J.; Malin, M. C.

1983-01-01

It is noted in the present consideration of the Venus lithosphere and its implications for plate tectonics that the major linear elevated regions of Venus, which are associated with Beta Regio and Aphrodite Terra, do not seem to have the shape required for sure interpretation as the divergent plate boundaries of seafloor spreading. Such tectonics instead appear to be confined to the median plains, and may not be resolvable in the Pioneer Venus altimetry data. The ratios of gravity anomalies to topographic heights indicate that surface load compensation occurs at depths greater than about 100 km under the western Aphrodite Terra and 400 km under Beta Regio, with at least some of this compensation probably being maintained by mantle convection. It is also found that the shape of Venus's hypsogram is very different from the ocean mode of the earth's hypsogram, and it is proposed that Venus tectonics resemble intraplate, basin-and-swell tectonics on earth.
Universal planetary tectonics (supertectonics)

NASA Astrophysics Data System (ADS)

Kochemasov, G. G.

2009-04-01

Universal planetary tectonics (supertectonics) G. Kochemasov IGEM of the Russian Academy of Sciences, Moscow, Russia, kochem.36@mail.ru The wave planetology [1-3 & others] proceeds from the following: "planetary structures are made by orbits and rotations". A uniform reason makes uniform structures. Inertia-gravity waves arising in planetary bodies due to their movements in Keplerian elliptical orbits with periodically changing accelerations warp these bodies in such way that they acquire polyhedron shapes (after interference of standing waves of four directions). Strong Newtonian gravity makes bodies larger than ~400 to 500 km in diameter globular and polyhedra are rarely seen. Only geomorphologic, geologic and geophysical mapping can develop these hidden structures. But small bodies, normally less than ~ 300 to 400 km in diameter, often show parts of the polyhedra, rarely fully developed forms (the asteroid Steins and satellite Amalthea present rather perfect forms of "diamond"). Depending on warping wavelengths (they make harmonics) various Plato's figures superimposed on each other can be distinguished. The fundamental wave 1 produces a tetrahedron, intrinsically dichotomic figure in which a vertex (contraction) always is opposed to a face (expansion). From the recent examples the best is the saturnian northern hexagon (a face) opposed to the southern hurricane (a vertex). The first overtone wave 2 is responsible for creation of structural octahedra. Whole ‘diamonds" and their parts are known [4, 5]. Other overtones produce less developed (because of smaller wave amplitudes) planetary shapes complicating main forms. Thus, the first common structural peculiarity of planetary bodies is their polyhedron nature. Not less important is the second common structural peculiarity. As all globular or smaller more or less isometric bodies rotate, they have an angular momentum. It is inevitably different in tropic and extra-tropic belts having uneven radii or distances to
Some aspects of active tectonism in Alaska as seen on ERTS-1

NASA Technical Reports Server (NTRS)

Gedney, L. D.; Vanwormer, J. D.

1973-01-01

ERTS-1 imagery is proving to be exceptionally useful in delineating structural features in Alaska which have never been recognized on the ground. Previously unmapped features such as seismically active faults and major structural lineaments are especially evident. Among the more significant results of this investigation is the discovery of an active strand of the Denali fault. The new fault has a history of scattered seismicity and was the scene of a magnitude 4.8 earthquake on October 1, 1972. Perhaps of greater significance is the disclosure of a large scale conjugate fracture system north of the Alaska Range. This fracture system appears to result from compressive stress radiating outward from around the outside of the great bend of the Alaska Range at Mt. McKinley.
A review of the tectonic evolution of the Northern Pacific and adjacent Cordilleran Orogen

NASA Astrophysics Data System (ADS)

Jakob, Johannes; Gaina, Carmen; Johnston, Stephen T.

2014-05-01

Numerous plate kinematic models for the North Pacific realm have been developed since the advent of plate tectonics in the early seventies (e.g Atwater (1970), Mammerickx and Sharman (1988)). Although published kinematic models are consistent with the broad scale features of the North Pacific, the link between plate motions and the evolution of the North American Cordillera remains poorly understood. Part of the problem lies in conflicting interpretations of geological versus paleomagnetic data sets, with the result being a lack of consensus regarding: the paleolocation of key geological units; the paleogeography of terrane formation and amalgamation; the motion, boundaries and even existence of oceanic plates; and the character (e.g. trend of subduction) and position of plate boundaries within the northern Pacific basin. Remnants of the Farallon and Kula plates, and some short-lived microplates, demonstrate the complicated tectonic evolution of the oceanic realm west of the North American margin (e.g. Rea and Dixon (1983); McCrory and Wilson (2013); Shephard et al. (2013)). The creation and destruction of major tectonic plates and microplates has presumably left a record in the Cordilleran orogen of western North America. However, working backward from the geological relationships to plate reconstructions remains difficult. Here we investigate the relationship between the plate motions of the Pacific Ocean and the terrane movements in the North American Cordillera by revising the marine magnetic and gravity anomalies of the northern Pacific. In particular, we reevaluate plate boundaries at times of major changes in plate geometry of the Pacific, Kula, Chinook and Farallon plates from C34n onward. Our focus is also on the plate geometries of the Resurrection, Eshamy and Siletz-Crescent plates during the time between anomaly C26 and C12, and the links between plate interactions and on-shore tectonic events recorded in the geological record of Vancouver Island

The Boundary of Tectonic Units of the South China Continent in the Meso-Neoproterozoic - Early Paleozoic: Insights from Integrated Geophysical Study

NASA Astrophysics Data System (ADS)

Guo, L.; Gao, R.; Meng, X.; Zhang, J.; Wang, H.; Liu, Y.

2013-12-01

The South China continent (SCC), located in the transition zone of the Eurasia, India and Pacific plates, formed in the Meso-Neoproterozoic by collision of the Yangtze block and the Cathaysia block. However, the boundaries of the two blocks before the late Paleozoic (from Meso-Neoproterozoic to early Paleozoic) remain debated in the literature due to strong and complex tectonic and magmatic activities since then. The south of Jiangnan archicontinent is covered mostly by the thick strata since the late Paleozoic, the surface of which is widely covered by the vegetation. And the regional tectonic deformation is extremely complicated with few basal outcrops. For decades, a variety of geophysical detections have been performed in the SCC for understanding the deep structure and tectonic evolution, including deep seismic sounding (DSS) profiles, magnetotelluric sounding (MT) profiles, gravity and magnetic surveys and a small amount of deep seismic reflection profiles. However, due to the limitations of resolution and accuracy of the observed geophysical data in the past, especially short of the deep seismic reflection profiles to reveal fine lithosphere structure, different scientists presented various views on the division of tectonic units in the SCC. In quite recent years, the SinoProbe-02 project launched a long profile of geophysical detections across the two blocks in the SCC, including deep seismic reflection, DSS, MT, and broadband seismic observation, the resolution and accuracy of which had been improved greatly. These newly data will benefit better understanding the deep structure and tectonic evolution of the SCC. Here, we assembled high-resolution Bouguer gravity anomalies and aeromagnetic anomalies data in the SCC. The magnetic data were reduced to the pole by used a varying magnetic inclinations algorithm. We then performed anomaly separation and multi-scales lineation structure analysis on the gravity and RTP magnetic data, and then did 3D fusion
Geodetic evidence for continuing tectonic activity of the Carboneras fault (SE Spain)

NASA Astrophysics Data System (ADS)

Echeverria, Anna; Khazaradze, Giorgi; Asensio, Eva; Masana, Eulalia

2015-11-01

The Carboneras fault zone (CFZ) is a prominent onshore-offshore strike-slip fault that forms part of the Eastern Betic Shear Zone (EBSZ), located in SE Spain. In this work, we show for the first time, the continuing tectonic activity of the CFZ and quantify its geodetic slip-rates using continuous and campaign GPS observations conducted during the last decade. We find that the left-lateral motion dominates the kinematics of the CFZ, with a strike-slip rate of 1.3 ± 0.2 mm/yr along the N48° direction. The shortening component is significantly lower and poorly constrained. Recent onshore and offshore paleoseismic and geomorphic results across the CFZ suggest a minimum Late Pleistocene to present-day strike-slip rate of 1.1 mm/yr. Considering the similarity of the geologic and geodetic slip rates measured at different points along the fault, the northern segment of the CFZ must have been slipping approximately at a constant rate during the Quaternary. Regarding the eastern Alpujarras fault zone corridor (AFZ), located to the north of the CFZ, our GPS measurements corroborate that this zone is active and exhibits a right-lateral motion. These opposite type strike-slip motion across the AFZ and CFZ is a result of a push-type force due to Nubia and Eurasia plate convergence, which, in turn, causes the westward escape of the block bounded by these two fault zones.
Extending Whole-earth Tectonics To The Terrestrial Planets

NASA Astrophysics Data System (ADS)

Baker, V. R.; Maruyama, S.; Dohm, J. M.

Based on the need to explain a great many geological and geophysical anomalies on Mars, and stimulated by the new results from the Mars Global Surveyor Mission, we propose a conceptual model of whole-EARTH (Episodic Annular Revolving Thermal Hydrologic) tectonics for the long-term evolution of terrestrial planets. The theory emphasizes (1) the importance of water in planetary evolution, and (2) the physi- cal transitions in modes of mantle convection in relation to planetary heat produc- tion. Depending on their first-order geophysical parameters and following accretion and differentiation from volatile-rich planetessimals, terrestrial planets should evolve through various stages of mantle convection, including magma ocean, plate tectonic, and stagnant lid processes. If a water ocean is able to condense from the planet's early steam atmosphere, an early regime of plate tectonics will follow the initial magma ocean. This definitely happened on earth, probably on Mars, and possibly on Venus. The Mars history led to transfer of large amounts of water to the mantle during the pe- riod of heavy bombardment. Termination of plate tectonics on Mars during the heavy bombardment period led to initiation of superplumes at Tharsis and Elysium, where long-persistent volcanism and water outbursts dominated much of later Martian his- tory. For Venus, warming of the early sun made the surface ocean unstable, eliminating its early plate-tectonic regime. Although Venus now experiences stagnant-lid convec- tion with episodic mantle overturns, the water subducted to its lower mantle during the ancient plate-tectonic regime manifests itself in the initation of volatile-rich plumes that dominate its current tectonic regime.
Using earthquake-triggered landslides as a hillslope-scale shear strength test: Insights into rock strength properties at geomorphically relevant spatial scales in high-relief, tectonically active settings

NASA Astrophysics Data System (ADS)

Gallen, Sean; Clark, Marin; Godt, Jonathan; Lowe, Katherine

2016-04-01

The material strength of rock is known to be a fundamental property in setting landscape form and geomorphic process rates as it acts to modulate feedbacks between earth surface processes, tectonics, and climate. Despite the long recognition of its importance in landscape evolution, a quantitative understanding of the role of rock strength in affecting geomorphic processes lags our knowledge of the influence of tectonics and climate. This gap stems largely from the fact that it remains challenging to quantify rock strength at the hillslope scale. Rock strength is strongly scale dependent because the number, size, spacing, and aperture of fractures sets the upper limit on rock strength, making it difficult to extrapolate laboratory measurements to landscape-scale interpretations. Here we present a method to determine near-surface rock strength at the hillslope-scale, relying on earthquake-triggered landslides as a regional-scale "shear strength" test. We define near-surface strength as the average strength of rock sample by the landslides, which is typically < 10 m. Based on a Newmark sliding block model, which approximates slope stability during an earthquake assuming a material with frictional and cohesive strength, we developed a coseismic landslide model that is capable of reproducing statistical characteristics of the distribution of earthquake-triggered landslides. We present results from two well-documented case-studies of earthquakes that caused widespread mass-wasting; the 2008 Mw 7.9 Wenchuan Earthquake, Sichuan Province, China and the 1994 Mw. 6.8 Northridge Earthquake, CA, USA. We show how this model can be used to determine near-surface rock strength and reproduce mapped landslide patterns provided the spatial distribution of local hillslope gradient, earthquake peak ground acceleration (PGA), and coseismic landsliding are well constrained. Results suggest that near-surface rock strength in these tectonically active settings is much lower than that
Tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere: observations in groundwaters along the San Andreas Fault

USGS Publications Warehouse

Deeds, Daniel A.; Kulongoski, Justin T.; Muhle, Jens; Weiss, Ray F.

2015-01-01

Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge (CreCre; ∼30 fmol kg−1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1–9 times CreCre), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10–980 times CreCre) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20–100 km) suggests that the SAFS potentially emits (0.3–1)×10−1 kg(0.3–1)×10−1 kg CF4 yr−1 to the Earth's surface. For comparison, the chemical weathering of ∼7.5×104 km2∼7.5×104 km2 of granitic rock in California is estimated to release (0.019–3.2)×10−1 kg(0.019–3.2)×10−1 kg CF4 yr−1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial–interglacial transitions.
Plate Tectonic Cycle. K-6 Science Curriculum.

ERIC Educational Resources Information Center

Blueford, J. R.; And Others

Plate Tectonics Cycle is one of the units of a K-6 unified science curriculum program. The unit consists of four organizing sub-themes: (1) volcanoes (covering formation, distribution, and major volcanic groups); (2) earthquakes (with investigations on wave movements, seismograms and sub-suface earth currents); (3) plate tectonics (providing maps…
Multifaulting in a tectonic syntaxis revealed by InSAR: The case of the Ziarat earthquake sequence (Pakistan)

NASA Astrophysics Data System (ADS)

Pinel-Puysségur, B.; Grandin, R.; Bollinger, L.; Baudry, C.

2014-07-01

On 28-29 October 2008, within 12 h, two similar Mw = 6.4 strike-slip earthquakes struck Baluchistan (Pakistan), as part of a complex seismic sequence. Interferometric Synthetic Aperture Radar (InSAR) data reveal that the peak of surface displacement is near the Ziarat anticline, a large active fold affected by Quaternary strike-slip faulting. All coseismic interferograms integrate the deformation due to both earthquakes. As their causative faults ruptured close to each other, the individual signals cannot be separated. According to their focal mechanisms, each earthquake may have activated a NE-SW sinistral or a NW-SE dextral fault segment, which leads to four possible scenarios of fault orientations. A nonlinear inversion of the InSAR data set allows rejecting two scenarios. The best slip distributions on the two fault segments for the two remaining scenarios are determined by linear inversion. Stress-change modeling favors a scenario involving two abutting conjugate strike-slip faults. Two other fault segments accommodated left-lateral strike slip during the seismic sequence. The activated fault system includes multiple fault segments with different orientations and little surface expression. This may highlight, at a smaller scale, the distributed, possibly transient character of deformation within a broader right-lateral shear zone. It suggests that the activated faults delineate a small tectonic block extruding and subtly rotating within the shear zone. It occurs in the vicinity of the local tectonic syntaxis where orogenic structures sharply turn around a vertical axis. These mechanisms could participate in the long-term migration of active tectonic structures within this kinematically unstable tectonic syntaxis.
Gravity and magnetic anomalies of the Cyprus arc and tectonic implications

NASA Astrophysics Data System (ADS)

Ergün, M.; Okay, S.; Sari, C.; Oral, E. Z.

2003-04-01

In present day, eastern Mediterranean is controlled by the collision of the African and Eurasian plates and displacements of Arabian, Anatolian and Aegean micro-plates. The boundary between African and Eurasian plates is delineated by the Hellenic arc and Pliny-Strabo trench in the west and the Cyprus arc and a diffuse fault system of the Eastern Anatolian Fault zone in the east. The available gravity and magnetic data from the easternmost Mediterranean allow to subdivide this basin into three provinces: the northeastern Mediterranean north of the Cyprus Arc; the Levant Basin south of the Cyprus Arc and east of the line that roughly continues the Suez rift trend toward the Gulf of Antalya, between Cyprus and Anaximander Mountains; and the Mediterranean Ridge, Herodotus Basin west of this line. High anomalies observed in Cyprus and the sea region at the south is prominent in the gravity data. The Bouguer gravity anomaly reaches its maximum values over Cyprus, where it is most probably caused by high dense Troodos ophiolites. The uplifted oceanic crust causes high Bouguer anomaly also seen in the vicinity of Eratosthenes Seamount. Another result obtained from gravity data is that the crust under Herodotos and Rhodes basins is somehow oceanic and Anaximander, Eratosthenes and Cyprus are continental fragments. There are no linear magnetic anomalies in the Mediterranean. But there are magnetic anomalies over the Eratosthenes seamount and as well as from Cyprus to the Antalya basin due to the ophiolitic bodies. In Cyprus, the last compressional deformations were defined near the Miocene/Pliocene boundary. The extensional deformation associated with the Antalya basin appears to be separated by a zone of the Florence rise and Anaximander Mountains affected by differential tectonic movements. Eratosthenes Seamount is a positive crustal feature in the process of collision with Cyprus along an active margin; there is clearly a potential tectonic relationship to the onland
Optimal Planet Properties For Plate Tectonics Through Time And Space

NASA Astrophysics Data System (ADS)

Stamenkovic, Vlada; Seager, Sara

2014-11-01

Both the time and the location of planet formation shape a rocky planet’s mass, interior composition and structure, and hence also its tectonic mode. The tectonic mode of a planet can vary between two end-member solutions, plate tectonics and stagnant lid convection, and does significantly impact outgassing and biogeochemical cycles on any rocky planet. Therefore, estimating how the tectonic mode of a planet is affected by a planet’s age, mass, structure, and composition is a major step towards understanding habitability of exoplanets and geophysical false positives to biosignature gases. We connect geophysics to astronomy in order to understand how we could identify and where we could find planet candidates with optimal conditions for plate tectonics. To achieve this goal, we use thermal evolution models, account for the current wide range of uncertainties, and simulate various alien planets. Based on our best model estimates, we predict that the ideal targets for plate tectonics are oxygen-dominated (C/O<1) (solar system like) rocky planets of ~1 Earth mass with surface oceans, large metallic cores super-Mercury, rocky body densities of ~7000kgm-3), and with small mantle concentrations of iron 0%), water 0%), and radiogenic isotopes 10 times less than Earth). Super-Earths, undifferentiated planets, and especially hypothetical carbon planets, speculated to consist of SiC and C, are not optimal for the occurrence of plate tectonics. These results put Earth close to an ideal compositional and structural configuration for plate tectonics. Moreover, the results indicate that plate tectonics might have never existed on planets formed soon after the Big Bang—but instead is favored on planets formed from an evolved interstellar medium enriched in iron but depleted in silicon, oxygen, and especially in Th, K, and U relative to iron. This possibly sets a belated Galactic start for complex Earth-like surface life if plate tectonics significantly impacts the build up
Tectonic and metamorphic discontinuities in the Greater Himalayan Sequence in Central Himalaya: in-sequence shearing by accretion from the Indian plate

NASA Astrophysics Data System (ADS)

Carosi, Rodolfo

2016-04-01

The Greater Himalayan Sequence (GHS) is the main metamorphic unit of the Himalayas, stretching for over 2400 km, bounded to the South by the Main Central Thrust (MCT) and to the North by the South Tibetan Detachment (STD) whose contemporanous activity controlled its exhumation between 23 and 17 Ma (Godin et al., 2006). Several shear zones and/or faults have been recognized within the GHS, usually regarded as out of sequence thrusts. Recent investigations, using a multitechnique approach, allowed to recognize a tectonic and metamorphic discontinuity, localized in the mid GHS, with a top-to-the SW sense of shear (Higher Himalayan Discontinuity: HHD) (Carosi et al., 2010; Montomoli et al., 2013). U-(Th)-Pb in situ monazite ages provide temporal constraint of the acitivity of the HHD from ~ 27-25 Ma to 18-17 Ma. Data on the P and T evolution testify that this shear zone affected the tectono-metamorphic evolution of the belt and different P and T conditions have been recorded in the hanging-wall and footwall of the HHD. The HHD is a regional tectonic feature running for more than 700 km, dividing the GHS in two different portions (Iaccarino et al., 2015; Montomoli et al., 2015). The occurrence of even more structurally higher contractional shear zone in the GHS (above the HHD): the Kalopani shear zone (Kali Gandaki valley, Central Nepal), active from ~ 41 to 30 Ma (U-Th-Pb on monazite) points out to a more complex deformation pattern in the GHS characterized by in sequence shearing. The actual proposed models of exhumation of the GHS, based exclusively on the MCT and STD activities, are not able to explain the occurrence of the HHD and other in-sequence shear zones. Any model of the tectonic and metamorphic evolution of the GHS should account for the occurrence of the tectonic and metamorphic discontinuities within the GHS and its consequences on the metamorphic paths and on the assembly of Himalayan belt. References Godin L., Grujic D., Law, R. D. & Searle, M. P. 2006
Magma-tectonic interactions in an area of active extension; a review of recent observations, models and interpretations from Iceland

NASA Astrophysics Data System (ADS)

Pedersen, Rikke; Sigmundsson, Freysteinn; Drouin, Vincent; Rafn Heimisson, Elías; Parks, Michelle; Dumont, Stéphanie; Árnadóttir, Þóra; Masterlark, Timothy; Ófeigsson, Benedíkt G.; Jónsdóttir, Kristín; Hooper, Andrew

2016-04-01

The geological setting of Iceland provides rich opportunities of studying magma-tectonic interactions, as it constitutes Earth's largest part of the mid-oceanic ridge system exposed above sea level. A series of volcanic and seismic zones accommodate the ~2 cm/year spreading between the North-American and Eurasian plates, and the Icelandic hot-spot conveniently provides the means of exposing this oceanic crust-forming setting above sea-level. Both extinct and active plumbing system structures can be studied in Iceland, as the deeply eroded tertiary areas provide views into the structures of extinct volcanic systems, and active processes can be inferred on in the many active volcanic systems. A variety of volcanic and tectonic processes cause the Icelandic crust to deform continuously, and the availability of contemporaneous measurements of crustal deformation and seismicity provide a powerful data set, when trying to obtain insight into the processes working at depth, such as magma migration through the uppermost lithosphere, magma induced host rock deformation and volcanic eruption locations and styles. The inferences geodetic and seismic datasets allow on the active plate spreading processes and subsurface magma movements in Iceland will be reviewed, in particular in relation to the Northern Volcanic Zone (NVZ). There the three phases of a rifting cycle (rifting, post-rifting, inter-rifting) have been observed. The NVZ is an extensional rift segment, bounded to the south by the Icelandic mantle plume, and to the north by the Tjörnes transform zone. The NVZ has typically been divided into five partly overlapping en-echelon fissure swarms, each with a central main volcanic production area. Most recently, additional insight into controlling factors during active rifting has been provided by the Bárðarbunga activity in 2014-2015 that included a major rifting event, the largest effusive eruption in Iceland since 1783, and a gradual caldera collapse. It is evident
An Intracratonic Record of North American Tectonics

NASA Astrophysics Data System (ADS)

Lovell, Thomas Rudolph

Investigating how continents change throughout geologic time provides insight into the underlying plate tectonic process that shapes our world. Researchers aiming to understand plate tectonics typically investigate records exposed at plate margins, as these areas contain direct structural and stratigraphic information relating to tectonic plate interaction. However, these margins are also susceptible to destruction, as orogenic processes tend to punctuate records of plate tectonics. In contrast, intracratonic basins are long-lived depressions located inside cratons, shielded from the destructive forces associated with the plate tectonic process. The ability of cratonic basins to preserve sedimentological records for extended periods of geologic time makes them candidates for recording long term changes in continents driven by tectonics and eustacy. This research utilizes an intracratonic basin to better understand how the North American continent has changed throughout Phanerozoic time. This research resolves geochronologic, thermochronologic, and sedimentologic changes throughout Phanerozoic time (>500 Ma) within the intracratonic Illinois Basin detrital record. Core and outcrop sampling provide the bulk of material upon which detrital zircon geochronologic, detrital apatite thermochronologic, and thin section petrographic analyses were performed. Geochronologic evidence presented in Chapters 2 and 3 reveal the Precambrian - Cretaceous strata of the intracratonic Illinois Basin yield three detrital zircon U-Pb age assemblages. Lower Paleozoic strata yield ages corresponding to predominantly cratonic sources (Archean - Mesoproterozoic). In contrast, Middle - Upper Paleozoic strata have a dominant Appalachian orogen (Neoproterozoic - Paleozoic) signal. Cretaceous strata yield similar ages to underlying Upper Paleozoic strata. We conclude that changes in the provenance of Illinois Basin strata result from eustatic events and tectonic forcings. This evidence
Anisotropy and tectonic deformation in the Ordos basin revealed by an active source seismic experiment

NASA Astrophysics Data System (ADS)

Jun, W. S.; Wang, F.; Xu, T.

2016-12-01

With the purpose of exploring the Ordos block, western North China Craton, two controlled-source deep seismic transects were conducted across this region. The first one is a 650 km long profile oriented N-S; the second is 1530 km and is oriented E-W. The upper mantle P wave-velocity derived from these profiles features a 0.25 km/s difference between them. Being the E-W higher that the N-S. The results obtained from both seismic profiles indicate that the upper mantle beneath the Ordos block presents seismic anisotropy in terms of discrepancy in Pn-wave velocity, such as the apparent seismic velocities observed along the two reference profiles demonstrate. This result is consistent with SKS-wave splitting measurements in the interior of the Ordos block. This indicates that the compressive stress state in Ordos during the Mesozoic became an extensional stress state in the Cenozoic. The high-velocity anomaly in the uppermost mantle under the west-east profile suggests that the lithospheric mantle is still not water-rich. Unlike what happened in the NCC to east of the Taihang Mountains, where the lithosphere experienced its thinning and destruction since the Mesozoic, the lithosphere in the interior of Ordos has suffered less deformation and remained tectonically stable. Keywords: wide-angle seismic profiling, Pn phase, high-velocity anomaly, upper mantle anisotropy, Ordos block, North China Craton. ReferencesChen L., 2009. Lithospheric structure variations between the eastern and central North China Craton from S- and P-receiver function migration. Phys. Earth Planet. Inter. 173, 216-227. Gao S., Rudnick R.L., Xu W.L., et al., 2008. Recycling deep cratonic lithosphere and generation of intraplate magmatism in the North China Craton. Earth Planet. Sci. Lett. 270, 41-53. Xu T., Zhang Z.J., Gao E.G., et al., 2010. Segmentally iterative ray tracing in complex 2D and 3D heterogeneous block models. Bull. Seism. Soc. Am. 100, 841-850. Zhu R.X., Zheng T.Y., 2009. Destruction
Tectonic, volcanic, and climatic geomorphology study of the Sierras Pampeanas Andes, northwestern Argentina

NASA Technical Reports Server (NTRS)

Bloom, A. L.; Strecker, M. R.; Fielding, E. J.

1984-01-01

A proposed analysis of Shuttle Imaging Radar-B (SIR-B) data extends current research in the Sierras Pampeanas and the Puna of northwestern Argentina to the determination - by the digital analysis of mountain-front sinuousity - of the relative age and amount of fault movement along mountain fronts of the late-Cenozoic Sierras Pampeanas basement blocks; the determination of the age and history of the boundary across the Andes at about 27 S latitude between continuing volcanism to the north and inactive volcanism to the south; and the determination of the age and extent of Pleistocene glaciation in the High Sierras, as well as the comparative importance of climatic change and tectonic movements in shaping the landscape. The integration of these studies into other ongoing geology projects contributes to the understanding of landform development in this active tectonic environment and helps distinguish between climatic and tectonic effects on landforms.
Palaeozoic and Mesozoic tectonic implications of Central Afghanistan

NASA Astrophysics Data System (ADS)

Sliaupa, Saulius; Motuza, Gediminas

2017-04-01

The field and laboratory studies were carried out in Ghor Province situated in the central part of Afghanistan. It straddles juxtaposition of the Tajik (alternatively, North Afghanistan) and Farah Rod blocks separated by Band-e-Bayan zone. The recent studies indicate that Band-e-Bayan zone represents highly tectonised margin of the Tajik block (Motuza, Sliaupa, 2016). The Band-e-Bayan zone is the most representative in terms of sedimentary record. The subsidence trends and sediment lithologies suggest the passive margin setting during (Cambrian?) Ordovician to earliest Carboniferous times. A change to the foredeep setting is implied in middle Carboniferous through Early Permian; the large-thickness flysh-type sediments were derived from continental island arc provenance, as suggested by chemical composition of mudtstones. This stage can be correlated to the amalgamation of the Gondwana supercontinent. The new passive-margin stage can be inferred in the Band-e-Bayan zone and Tajik blocks in the Late Permian throughout the early Late Triassic that is likely related to breaking apart of Gondwana continent. A collisional event is suggested in latest Triassic, as seen in high-rate subsidence associating with dramatic change in litholgies, occurrence of volcanic rocks and granidoid intrusions. The continental volcanic island arc derived (based on geochemical indices) terrigens prevail at the base of Jurassic that were gradually replaced by carbonate platform in the Middle Jurassic pointing to cessation of the tectonic activity. A new tectonic episode (no deposition; and folding?) took place in the Tajik and Band-e-Bayan zone in Late Jurassic. The geological section of the Farah Rod block, situated to the south, is represented by Jurassic and Cretaceous sediments overlain by sporadic Cenozoic volcanic-sedimentary succession. The lower part of the Mesozoic succession is composed of terrigenic sediments giving way to upper Lower Cretaceous shallow water carbonates implying
Tectonic implications of facies patterns, Lower Permian Dry Mountain trough, east-central Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallegos, D.M.; Snyder, W.S.; Spinosa, C.

1991-02-01

Paleozoic tectonism is indicated by a study of a west-east facies analysis transect across the northern portion of the Lower Permian Dry Mountain trough (DMT). In an attempt to characterize the Early Permian basin-filling sequences, three broadly recognizable facies packages have been identified across the DMT: the western margin facies and the central basin facies of the DMT and an eastern shelf facies. In the western margin facies of the basin, pulses of tectonic activity are recorded at McCloud Spring in the Sulphur Springs Range. Here, shallow open-marine carbonate overlies eroded Vinini Formation and, in turn, is unconformably overlain bymore » basinal marine carbonate. An unconformity also marks the contact with the overriding prograding coarse clastic facies. These abrupt transitions suggest the sediments were deposited in a tectonically active area where they preservation of Waltherian sequences is unlikely to occur. Similarly abrupt transitions are evident in the western part of the central basin facies. At Portuguese Springs n the Diamond Range, a thin basal marine conglomerate delineates Lower Permian sedimentation over the Pennsylvanian Ely Formation. Coarsening-upward basinal carbonate strata of pelagic, hemipelagic, and turbidite components overlie the basal conglomerate. this progression of sediments is unconformably overlain by a subaerial sequence of coarse clastic deposits. Within the eastern part of the central basin facies in the Maverick Spring Range, the Lower Permian sediments are open-marine siltstone, wackestone, packstone, and grainstone. The sediments are assigned to a gradually sloping ramp, indicating the effects of tectonism on this margin of the basin were subdued.« less
Kasei Vallis of Mars: Dating the Interplay of Tectonics and Geomorphology

NASA Technical Reports Server (NTRS)

Wise, D. U.

1985-01-01

Crater density age dates on more than 250 small geomorphic surfaces in the Kasei Region of Mars show clusterings indicative of times of peak geomorphic and tectonic activity. Kasei Vallis is part of a 300 km wide channel system breaching a N-S trending ancient basement high (+50,000 crater age) separating the Chryse Basin from the Tharsis Volcanic Province of Mars. The basement high was covered by a least 3 groups of probable volcanic deposits. Major regional fracturing took place at age 4,000 to 5,000 and was immediately followed by deposition of regional volcanics of the Fesenkov Plains (age 3,000 to 4,200). Younger clusterings of dates in the 900 to 1,500 and 500 to 700 range represent only minor modification of the basic tectonic geomorphic landform. The data suggest that Kasei gap is a structurally controlled breach of a buried ridge by a rather brief episode of fluvial activity.
Tectonic evolution of the Troodos Ophiolite within the Tethyan Framework

NASA Astrophysics Data System (ADS)

Dilek, Yildirim; Thy, Peter; Moores, Eldridge M.; Ramsden, Todd W.

1990-08-01

A new tectonic model reconciles conflicting structural and geochemical evidence for the origin of the Troodos ophiolite, a well-preserved remnant of Neotethyan oceanic crust. Grabens and normal faults within the sheeted dike complex and the extrusive sequence of the Troodos ophiolite resemble those of oceanic spreading centers. Diverse intrusive and tectonic contact relationships between the sheeted dike complex and the underlying plutonic sequence indicate multiple and episodic intrusion of magma and along- and across-strike variation in volcanic and tectonic activity during development of oceanic crust. Coupled with the existence of the Arakapas transform fault to the south, these structural and intrusive relationships suggest origin at an intersection between a spreading center and a transform fault. The arclike chemistry of sheeted dikes and related extrusive rocks and the inferred highly depleted and hydrous nature of the mantle source of the late stage intrusive and extrusive rocks argue, however, for generation of part of the ophiolite within a subduction zone environment. Regional reconstructions suggest that the Mesozoic Neotethys may have evolved as a marginal basin both to the Afro-Arabian continent and the Paleotethyan ocean over an active or recently active south dipping subduction zone. The Troodos ophiolite and other eastern Mediterranean ophiolites, whose magma compositions were affected by the subducted Paleotethyan slab, may have formed along east-west trending spreading centers separated by north-south trending transform faults within this marginal basin. A rapid change in relative plate motion in late Cretaceous time between Eurasia and Afro-Arabia created a regional compressive regime that may have resulted in plate boundary reorganizations within the Neotethyan realm and in initiation of north dipping subduction zone(s) beneath the Troodos and other ophiolites in the region. The apparent forearc setting of the Troodos ophiolite is a
The Potential for Volcanism and Tectonics on Extrasolar Terrestrial Planets

NASA Astrophysics Data System (ADS)

Quick, Lynnae C.; Roberge, Aki

2018-01-01

JWST and other next-generation space telescopes (e.g., LUVOIR, HabEx, & OST) will usher in a new era of exoplanet characterization that may lead to the identification of habitable, Earth-like worlds. Like the planets and moons in our solar system, the surfaces and interiors of terrestrial exoplanets may be shaped by volcanism and tectonics (Fu et al., 2010; van Summeren et al., 2011; Henning and Hurford, 2014). The magnitude and rate of occurrence of these dynamic processes can either facilitate or preclude the existence of habitable environments. Likewise, it has been suggested that detections of cryovolcanism on icy exoplanets, in the form of geyser-like plumes, could indicate the presence of subsurface oceans (Quick et al., 2017).The presence of volcanic and tectonic activity on solid exoplanets will be intimately linked to planet size and heat output in the form of radiogenic and/or tidal heating. In order to place bounds on the potential for such activity, we estimated the heat output of a variety of exoplanets observed by Kepler. We considered planets whose masses and radii range from 0.067 ME (super-Ganymede) to 8 ME (super-Earth), and 0.5 to 1.8 RE, respectively. These heat output estimates were then compared to those of planets, moons, and dwarf planets in our solar system for which we have direct evidence for the presence/absence of volcanic and tectonic activity. After exoplanet heating rates were estimated, depths to putative molten layers in their interiors were also calculated. For planets such as TRAPPIST-1h, whose densities, orbital parameters, and effective temperatures are consistent with the presence of significant amounts of H2O (Luger et al., 2017), these calculations reveal the depths to internal oceans which may serve as habitable niches beneath surface ice layers.
Recent and active tectonics of the external zone of the Northern Apennines (Italy)

NASA Astrophysics Data System (ADS)

Boccaletti, Mario; Corti, Giacomo; Martelli, Luca

2011-08-01

We present a comprehensive study of the recent and active tectonics of the external part of the Northern Apennines (Italy) by using morphotectonic, geological-structural, and stratigraphic analysis, compared with the current seismicity of the region. This analysis suggests that the external part of the Northern Apennines is characterised by presence of three major systems of Quaternary compressive structures corresponding to (1) the Apenninic watershed, (2) the Apennines-Po Plain margin (pede-Apenninic thrust front), and (3) the Emilia, Ferrara, and Adriatic Fold systems buried below the Po Plain. Geological data and interpreted seismic sections indicate a roughly N-S Quaternary deformation direction, with rates <2.5 mm/year. The shortening decreased since the Pliocene, when our data indicate compression in a NNW-SSE direction and rates up to 7 mm/year. The trend and kinematics of the structures affecting the Apennines-Po Plain margin and the Po Plain subsoil fit well the pattern of the current seismicity of the area, as well as recent GPS and geodetic levelling data, pointing to a current activity of these thrust systems controlled by an overall compressive stress field. Close to the Apenninic watershed, earthquake focal mechanisms indicate that shallow extension is associated to deep compression. The extensional events may be related to a secondary extensional stress field developing on the hangingwall of the thrust system affecting the Apenninic watershed; alternatively, this thrust system may have been recently deactivated and overprinted by active normal faulting. Deeper compressive events are related to the activity of both a major basement thrust that connects at surface with the pede-Apenninic thrust front and a major Moho structure.

Tectonic History of the Terrestrial Planets

NASA Technical Reports Server (NTRS)

Solomon, Sean C.

1993-01-01

The topics covered include the following: patterns of deformation and volcanic flows associated with lithospheric loading by large volcanoes on Venus; aspects of modeling the tectonics of large volcanoes on the terrestrial planets; state of stress, faulting, and eruption characteristics of large volcanoes on Mars; origin and thermal evolution of Mars; geoid-to-topography ratios on Venus; a tectonic resurfacing model for Venus; the resurfacing controversy for Venus; and the deformation belts of Lavinia Planitia.
10 CFR 960.4-2-7 - Tectonics.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Tectonics. 960.4-2-7 Section 960.4-2-7 Energy DEPARTMENT OF ENERGY GENERAL GUIDELINES FOR THE PRELIMINARY SCREENING OF POTENTIAL SITES FOR A NUCLEAR WASTE REPOSITORY Postclosure Guidelines § 960.4-2-7 Tectonics. (a) Qualifying condition. The site shall be located...
Stability of active mantle upwelling revealed by net characteristics of plate tectonics.

PubMed

Conrad, Clinton P; Steinberger, Bernhard; Torsvik, Trond H

2013-06-27

Viscous convection within the mantle is linked to tectonic plate motions and deforms Earth's surface across wide areas. Such close links between surface geology and deep mantle dynamics presumably operated throughout Earth's history, but are difficult to investigate for past times because the history of mantle flow is poorly known. Here we show that the time dependence of global-scale mantle flow can be deduced from the net behaviour of surface plate motions. In particular, we tracked the geographic locations of net convergence and divergence for harmonic degrees 1 and 2 by computing the dipole and quadrupole moments of plate motions from tectonic reconstructions extended back to the early Mesozoic era. For present-day plate motions, we find dipole convergence in eastern Asia and quadrupole divergence in both central Africa and the central Pacific. These orientations are nearly identical to the dipole and quadrupole orientations of underlying mantle flow, which indicates that these 'net characteristics' of plate motions reveal deeper flow patterns. The positions of quadrupole divergence have not moved significantly during the past 250 million years, which suggests long-term stability of mantle upwelling beneath Africa and the Pacific Ocean. These upwelling locations are positioned above two compositionally and seismologically distinct regions of the lowermost mantle, which may organize global mantle flow as they remain stationary over geologic time.
Tsunamis from Tectonic Sources along Caribbean Plate Boundaries

NASA Astrophysics Data System (ADS)

Lopez, A. M.; Chacon, S.; Zamora, N.; Audemard, F. A.; Dondin, F. J. Y.; Clouard, V.; Løvholt, F.; Harbitz, C. B.; Vanacore, E. A.; Huerfano Moreno, V. A.

2015-12-01

The Working Group 2 (WG2) of the Intergovernmental Coordination Group for the Tsunami and Other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (ICG/CARIBE-EWS) in charge of Tsunami Hazards Assessment, has generated a list of tsunami sources for the Caribbean region. Simulating these worst-case, most credible scenarios would provide an estimate of the resulting effects on coastal areas within the Caribbean. In the past few years, several publications have addressed this issue resulting in a collection of potential tsunami sources and scenarios. These publications come from a wide variety of sources; from government agencies to academic institutions. Although these provide the scientific community with a list of sources and scenarios, it was the interest of the WG2 to evaluate what has been proposed and develop a comprehensive list of sources, therefore leaving aside proposed scenarios. The seismo-tectonics experts of the Caribbean within the WG2 members were tasked to evaluate comprehensively which published sources are credible, worst-cases, and consider other sources that have been omitted from available reports. Among these published sources are the GEM Faulted Earth Subduction Characterization Project, and the LANTEX/Caribe Wave annual exercise publications (2009-2015). Caribbean tectonic features capable of generating tsunamis from seismic dislocation are located along the Northeastern Caribbean, the Lesser Antilles Trench, and the Panamá and Southern Caribbean Deformed Belts. The proposed sources have been evaluated based on historical and instrumental seismicity as well as geological and geophysical studies. This paper presents the sources and their justification as most-probable tsunami sources based on the context of crustal deformation due to Caribbean plate interacting with neighboring North and South America plates. Simulations of these sources is part of a subsequent phase in which effects of these tectonically induced tsunamis
Surface-wave potential for triggering tectonic (nonvolcanic) tremor-corrected

USGS Publications Warehouse

Hill, David P.

2012-01-01

Source processes commonly posed to explain instances of remote dynamic triggering of tectonic (nonvolcanic) tremor by surface waves include frictional failure and various modes of fluid activation. The relative potential for Love- and Rayleigh-wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike-slip faults under the Coulomb-Griffith failure criteria as a function of incidence angle are anticorrelated over the 15- to 30-km-depth range that hosts tectonic tremor. Love-wave potential is high for strike-parallel incidence on low-angle reverse faults and null for strike-normal incidence; the opposite holds for Rayleigh waves. Love-wave potential is high for both strike-parallel and strike-normal incidence on vertical, strike-slip faults and minimal for ~45° incidence angles. The opposite holds for Rayleigh waves. This pattern is consistent with documented instances of tremor triggered by Love waves incident on the Cascadia megathrust and the San Andreas fault (SAF) in central California resulting from shear failure on weak faults (apparent friction is μ* ≤ 0:2). Documented instances of tremor triggered by surface waves with strike-parallel incidence along the Nankai megathrust beneath Shikoku, Japan, however, are associated primarily with Rayleigh waves. This is consistent with the tremor bursts resulting from mixed-mode failure (crack opening and shear failure) facilitated by near-lithostatic ambient pore pressure, low differential stress, with a moderate friction coefficient (μ ~ 0:6) on the Nankai subduction interface. Rayleigh-wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process, except perhaps for an indirect role on the SAF in sustaining tremor into the Rayleigh-wave coda that was initially triggered by Love waves.
Impacts and tectonism in Earth and moon history of the past 3800 million years

NASA Technical Reports Server (NTRS)

Stothers, Richard B.

1992-01-01

The moon's surface, unlike the Earth's, displays a comparatively clear record of its past bombardment history for the last 3800 Myr, the time since active lunar tectonism under the massive premare bombardment ended. From Baldwin's (1987) tabulation of estimated ages for a representative sample of large lunar craters younger than 3800 Ma, six major cratering episodes can be discerned. These six bombardment episodes, which must have affected the Earth too, appear to match in time the six major episodes of orogenic tectonism on Earth, despite typical resolution errors of +/- 100 Myr and the great uncertainties of the two chronologies. Since more highly resolved events during the Cenozoic and Mesozoic Eras suggest the same correlation, it is possible that large impacts have influenced plate tectonics and other aspects of geologic history, perhaps by triggering flood basalt eruptions.
Rheology, tectonics, and the structure of the Venus lithosphere

NASA Technical Reports Server (NTRS)

Zuber, M. T.

1994-01-01

Given the absence of ground truth information on seismic structure, heat flow, and rock strength, or short wavelength gravity or magnetic data for Venus, information on the thermal, mechanical and compositional nature of the shallow interior must be obtained by indirect methods. Using pre-Magellan data, theoretical models constrained by the depths of impact craters and the length scales of tectonic features yielded estimates on the thickness of Venus' brittle-elastic lithosphere and the allowable range of crustal thickness and surface thermal gradient. The purpose of this study is to revisit the question of the shallow structure of Venus based on Magellan observations of the surface and recent experiments that address Venus' crustal rheology.
Seismic source study of the Racha-Dzhava (Georgia) earthquake from aftershocks and broad-band teleseismic body-wave records: An example of active nappe tectonics

USGS Publications Warehouse

Fuenzalida, H.; Rivera, L.; Haessler, H.; Legrand, D.; Philip, H.; Dorbath, L.; McCormack, D.; Arefiev, S.; Langer, C.; Cisternas, A.

1997-01-01

-S oriented plane. Nappe tectonics has been identified as an important feature in the Caucasus, and the source mechanism is consistent with this observation. A hidden fault is present below the nappe, and no large surface breaks were observed due to the main shock. The epicentral region is characterized by sediments that are trapped between two crystalline basements: the Dzirula Massif, which crops out south of Chiatoura, and the Caucasus Main Range north of Oni. Most, if not all, of the rupture is controlled by the thrusting of overlapping, deformed and folded sediments over the Dzirula Massif. This event is another example of blind active faults, with the distinctive feature that the fault plane dips at a gentle angle. The Racha Range is one of the surface expressions of this blind thrust, and its growth is the consequence and evidence of similar earthquakes in the past.
Neotectonics and geomorphic evolution of the northwestern arm of the Yellowstone Tectonic Parabola: Controls on intra-cratonic extensional regimes, southwest Montana

USGS Publications Warehouse

Ruleman, Chester A.; Larsen, Mort; Stickney, Michael C.

2014-01-01

The catastrophic Hebgen Lake earthquake of 18 August 1959 (MW 7.3) led many geoscientists to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system and adjacent Hebgen Lake–Red Canyon fault system provide an intermountain active tectonic analog for regional analyses of extensional crustal deformation. The Madison Range fault system comprises fault zones (~100 km in length) that have multiple salients and embayments marked by preexisting structures exposed in the footwall. Quaternary tectonic activity rates differ along the length of the fault system, with less displacement to the north. Within the Hebgen Lake basin, the 1959 earthquake is the latest slip event in the Hebgen Lake–Red Canyon fault system and southern Madison Range fault system. Geomorphic and paleoseismic investigations indicate previous faulting events on both fault systems. Surficial geologic mapping and historic seismicity support a coseismic structural linkage between the Madison Range and Hebgen Lake–Red Canyon fault systems. On this trip, we will look at Quaternary surface ruptures that characterize prehistoric earthquake magnitudes. The one-day field trip begins and ends in Bozeman, and includes an overview of the active tectonics within the Madison Valley and Hebgen Lake basin, southwestern Montana. We will also review geologic evidence, which includes new geologic maps and geomorphic analyses that demonstrate preexisting structural controls on surface rupture patterns along the Madison Range and Hebgen Lake–Red Canyon fault systems.
Feature Selection in Classification of Eye Movements Using Electrooculography for Activity Recognition

PubMed Central

Mala, S.; Latha, K.

2014-01-01

Activity recognition is needed in different requisition, for example, reconnaissance system, patient monitoring, and human-computer interfaces. Feature selection plays an important role in activity recognition, data mining, and machine learning. In selecting subset of features, an efficient evolutionary algorithm Differential Evolution (DE), a very efficient optimizer, is used for finding informative features from eye movements using electrooculography (EOG). Many researchers use EOG signals in human-computer interactions with various computational intelligence methods to analyze eye movements. The proposed system involves analysis of EOG signals using clearness based features, minimum redundancy maximum relevance features, and Differential Evolution based features. This work concentrates more on the feature selection algorithm based on DE in order to improve the classification for faultless activity recognition. PMID:25574185
Feature selection in classification of eye movements using electrooculography for activity recognition.

PubMed

Mala, S; Latha, K

2014-01-01

Activity recognition is needed in different requisition, for example, reconnaissance system, patient monitoring, and human-computer interfaces. Feature selection plays an important role in activity recognition, data mining, and machine learning. In selecting subset of features, an efficient evolutionary algorithm Differential Evolution (DE), a very efficient optimizer, is used for finding informative features from eye movements using electrooculography (EOG). Many researchers use EOG signals in human-computer interactions with various computational intelligence methods to analyze eye movements. The proposed system involves analysis of EOG signals using clearness based features, minimum redundancy maximum relevance features, and Differential Evolution based features. This work concentrates more on the feature selection algorithm based on DE in order to improve the classification for faultless activity recognition.
Overview of geology and tectonic evolution of the Baikal-Tuva area.

PubMed

Gladkochub, Dmitry; Donskaya, Tatiana

2009-01-01

This chapter provides the results of geological investigations of the main tectonic units of the Baikal-Tuva region (southwestern part of Siberia) during the last decades: the ancient Siberian craton and adjacent areas of the Central Asian Orogenic belt. In the framework of these main units we describe small-scale blocks (terranes) with focus on details of their inner structure and evolution through time. As well as describing the geology and tectonics of the area studied, we give an overview of underwater sediments, neotectonics, and some phenomena of history and development of the Baikal, Khubsugul, Chargytai, and Tore-Chol Lakes basins of the Baikal-Tuva region. It is suggested that these lakes' evolution was controlled by neotectonic processes, modern seismic activity, and global climate changes.
Tectonic evolution of the Qumran Basin from high-resolution 3.5-kHz seismic profiles and its implication for the evolution of the northern Dead Sea Basin

NASA Astrophysics Data System (ADS)

Lubberts, Ronald K.; Ben-Avraham, Zvi

2002-02-01

The Dead Sea Basin is a morphotectonic depression along the Dead Sea Transform. Its structure can be described as a deep rhomb-graben (pull-apart) flanked by two block-faulted marginal zones. We have studied the recent tectonic structure of the northwestern margin of the Dead Sea Basin in the area where the northern strike-slip master fault enters the basin and approaches the western marginal zone (Western Boundary Fault). For this purpose, we have analyzed 3.5-kHz seismic reflection profiles obtained from the northwestern corner of the Dead Sea. The seismic profiles give insight into the recent tectonic deformation of the northwestern margin of the Dead Sea Basin. A series of 11 seismic profiles are presented and described. Although several deformation features can be explained in terms of gravity tectonics, it is suggested that the occurrence of strike-slip in this part of the Dead Sea Basin is most likely. Seismic sections reveal a narrow zone of intensely deformed strata. This zone gradually merges into a zone marked by a newly discovered tectonic depression, the Qumran Basin. It is speculated that both structural zones originate from strike-slip along right-bending faults that splay-off from the Jordan Fault, the strike-slip master fault that delimits the active Dead Sea rhomb-graben on the west. Fault interaction between the strike-slip master fault and the normal faults bounding the transform valley seems the most plausible explanation for the origin of the right-bending splays. We suggest that the observed southward widening of the Dead Sea Basin possibly results from the successive formation of secondary right-bending splays to the north, as the active depocenter of the Dead Sea Basin migrates northward with time.
Venus tectonic styles and crustal differentiation

NASA Technical Reports Server (NTRS)

Kaula, W. M.; Lenardic, A.

1992-01-01

Two of the most important constraints are known from Pioneer Venus data: the lack of a system of spreading rises, indicating distributed deformation rather than plate tectonics; and the high gravity/topography ratio, indicating the absence of an asthenosphere. In addition, the high depth/diameter ratios of craters on Venus indicate that Venus probably has no more crust than Earth. The problems of the character of tectonics and crustal formation and recycling are closely coupled. Venus appears to lack a recycling mechanism as effective as subduction, but may also have a low rate of crustal differentiation because of a mantle convection pattern that is more distributed, less concentrated, than Earth's. Distributed convection, coupled with the nonlinear dependence of volcanism on heat flow, would lead to much less magmatism, despite only moderately less heat flow, compared to Earth. The plausible reason for this difference in convective style is the absence of water in the upper mantle of Venus. We have applied finite element modeling to problems of the interaction of mantle convection and crust on Venus. The main emphasis has been on the tectonic evolution of Ishtar Terra, as the consequence of convergent mantle flow. The early stage evolution is primarily mechanical, with crust being piled up on the down-stream side. Then the downflow migrates away from the center. In the later stages, after more than 100 m.y., thermal effects develop due to the insulating influence of the thickened crust. An important feature of this modeling is the entrainment of some crustal material in downflows. An important general theme in both convergent and divergent flows is that of mixing vs. stratification. Models of multicomponent solid-state flow obtain that lower-density crustal material can be entrained and recycled, provided that the ration of low-density to high-density material is small enough (as in subducted slabs on Earth). The same considerations should apply in upflows; a
Looking for Plate Tectonics in all the wrong fluids

NASA Astrophysics Data System (ADS)

Davaille, Anne

2017-04-01

Ever since the theory of Plate Tectonics in the 1960's, the dream of the geomodeler has been to generate plate tectonics self-consistently from thermal convection in the laboratory. By selfconsistenly, I mean that the configuration of the plate boundaries is in no way specified a priori, so that the plates develop and are wholly consumed without intervention from the modeler. The reciepe is simple : put a well-chosen fluid in a fishtank heated from below and cooled from above, wait and see. But the « well-chosen » is the difficult part... and the interesting one. Plate tectonics is occuring on Earth because of the characteristics of the lithosphere rheology. The latter are complex to estimate as they depend on temperature, pressure, phase, water content, chemistry, strain rate, memory and scale. As a result, the ingredients necessary for plate tectonics are still debated, and it would be useful to find an analog fluid who could reproduce plate tectonics in the laboratory. I have therefore spent the last 25 years to try out fluids, and I shall present a number of failures to generate plate tectonics using polymers, colloids, ketchup, milk, chocolate, sugar, oils. To understand why they failed is important to narrow down the « well-chosen » fluid.
Influence of time and length size feature selections for human activity sequences recognition.

PubMed

Fang, Hongqing; Chen, Long; Srinivasan, Raghavendiran

2014-01-01

In this paper, Viterbi algorithm based on a hidden Markov model is applied to recognize activity sequences from observed sensors events. Alternative features selections of time feature values of sensors events and activity length size feature values are tested, respectively, and then the results of activity sequences recognition performances of Viterbi algorithm are evaluated. The results show that the selection of larger time feature values of sensor events and/or smaller activity length size feature values will generate relatively better results on the activity sequences recognition performances. © 2013 ISA Published by ISA All rights reserved.
Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: characteristics, extent, and tectonic significance

USGS Publications Warehouse

Tull, James; Holm-Denoma, Christopher S.; Barineau, Clinton I.

2014-01-01

Fault-dismembered segments of a distinctive, extensive, highly allochthonous, and tectonically significant Ordovician (ca. 480–460 Ma) basin, which contains suites of bimodal metavolcanic rocks, associated base metal deposits, and thick immature deep-water (turbiditic) metasediments, occur in parts of the southern Appalachian Talladega belt, eastern Blue Ridge, and Inner Piedmont of Alabama, Georgia, and North and South Carolina. The basin's predominantly metasedimentary strata display geochemical and isotopic evidence of a mixed provenance, including an adjacent active volcanic arc and a provenance of mica (clay)-rich sedimentary and felsic plutonic rocks consistent with Laurentian (Grenvillian) upper-crustal continental rocks and their passive-margin cover sequences. Geochemical characteristics of the subordinate intercalated bimodal metavolcanic rocks indicate formation in a suprasubduction environment, most likely a back-arc basin, whereas characteristics of metasedimentary units suggest deposition above Neoproterozoic rift and outer-margin lower Paleozoic slope and rise sediments within a marginal basin along Ordovician Laurentia's Iapetus margin. This tectonic setting indicates that southernmost Appalachian Ordovician orogenesis (Taconic orogeny) began as an extensional accretionary orogen along the outer margin of Laurentia, rather than in an exotic (non-Laurentian) arc collisional setting. B-type subduction polarity requires that the associated arc-trench system formed southeast of the palinspastic position of the back-arc basin. This scenario can explain several unique features of the southern Appalachian Taconic orogen, including: the palinspastic geographic ordering of key tectonic elements (i.e., back-arc, arc, etc.), and a lack of (1) an obducted arc sensu stricto on the Laurentian margin, (2) widespread Ordovician regional metamorphism, and (3) Taconic klippen to supply detritus to the Taconic foreland basin.
Traces of warping subsided tectonic blocks on Miranda, Enceladus, Titan

NASA Astrophysics Data System (ADS)

Kochemasov, G.

2007-08-01

sharp difference between uplifted and subsided blocks presents Miranda having very sharp relief range. Subsided areas (coronas) are strongly folded, uplifted areas strongly degassed what was witnessed by numerous craters of various sizes (not all craters are of impact origin!). Coronas on Miranda present subsided segment and sectors. Typical is a very sharp boundary between risen (+) and fallen (-) blocks. On Enceladus the subsided (squeezed) southern pole area is characterized by "tiger stripes" - traces of contraction, young ice deposits and famous ejections of water vapor and ice. The squeezed area expels 'molten" material from interior - compare with periodically active Hawaiian volcano expelling basalts from constantly under contraction Pacific basin interior. As to the subsided Pacific basin, it is antepodean to uplifted deeply cracked and degassing Africa. On Enceladus to contracted south is opposed expanded north where past degassing is witnessed by numerous craters (not all of them are impacts!). Contraction traces are very impressive on subsided Titan's surfaces - methane filled thinly folded huge areas mainly in near equatorial regions (some scientists think that these folds are eolian dunes but they are parallel, not perpendicular to presumed winds and, besides, winds below ˜60 km in Titan's atmosphere are not detected by "Huygens") [1, 2]. This methane rich area of intensive folding is antepodean to the uplifted and mainly composed of water ice region Xanadu cut by numerous tectonically controlled dry "valleys". So, in spite of many varieties of surface features on icy satellites of the outer Solar system a common main tectonic tendency exists: opposition of subsided contracted and uplifted expanded blocks. References: [1] Kochemasov G.G. (2006)Titan's radar images: crosscutting ripples are dunes or warping surface waves?// Berlin, 22-26 Sept. 2006, EUROPLANET Sci. Conf. 1, EPSC2006-A-00045. [2] Kochemasov G.G. (2006)Planetary plains: subsidence and
Generation and Initiation of Plate Tectonics on Terrestrail Planets

NASA Astrophysics Data System (ADS)

Foley, Bradford J.

The question of why plate tectonics occurs on Earth, but not on the other planets of our solar system, is one of the most fundamental issues in geophysics and planetary science. I study this problem using numerical simulations of mantle convection with a damage-grainsize feedback (grain-damage) to constrain the conditions necessary for plate tectonics to occur on a terrestrial planet, and how plate tectonics initiates. In Chapter 2, I use numerical simulations to determine how large a viscosity ratio, between pristine lithosphere and mantle, damage can offset to allow mobile (plate-like) convection. I then use the numerical results to formulate a new scaling law to describe the boundary between stagnant lid and plate-like regimes of mantle convection. I hypothesize that damage must reduce the viscosity of shear zones in the lithosphere to a critical value, equivalent to the underlying mantle viscosity, in order for plate tectonics to occur, and demonstrate that a scaling law based on this hypothesis reproduces the numerical results. For the Earth, damage is efficient in the lithosphere and provides a viable mechanism for the operation of plate tectonics. I apply my theory to super-Earths and map out the transition between plate-like and stagnant lid convection with a "planetary plate-tectonic phase" diagram in planet size-surface temperature space. Both size and surface temperature are important, with plate tectonics being favored for larger, cooler planets. This gives a natural explanation for Earth, Venus, and Mars, and implies that plate tectonics on exoplanets should correlate with size, incident solar radiation, and atmospheric composition. In Chapters 3 and 4 I focus on the initiation of plate tectonics. In Chapter 3, I develop detailed scaling laws describing plate speed and heat flow for mantle convection with grain-damage across a wide parameter range, with the intention of applying these scaling laws to the early Earth in Chapter 4. Convection with grain
Plate Tectonics: The Way the Earth Works. Teacher's Guide. LHS GEMS.

ERIC Educational Resources Information Center

Cuff, Kevin

This teacher guide presents a unit on plate tectonics and introduces hands-on activities for students in grades 6-8. In each unit, students act as real scientists and gather evidence by using science process skills such as observing, graphing, analyzing data, designing and making models, visualizing, communicating, theorizing, and drawing…

Habitability from Tidally Induced Tectonics

NASA Astrophysics Data System (ADS)

Valencia, Diana; Tan, Vivian Yun Yan; Zajac, Zachary

2018-04-01

The stability of Earth’s climate on geological timescales is enabled by the carbon–silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and outgassing of atmospheric carbon. On Earth, this thermostat is enabled by plate tectonics that sequesters outgassed CO2 back into the mantle via weathering and subduction at convergent margins. Here we propose a separate tectonic mechanism—vertical recycling—that can serve as the vehicle for CO2 outgassing and sequestration over long timescales. The mechanism requires continuous tidal heating, which makes it particularly relevant to planets in the habitable zone of M stars. Dynamical models of this vertical recycling scenario and stability analysis show that temperate climates stable over timescales of billions of years are realized for a variety of initial conditions, even as the M star dims over time. The magnitude of equilibrium surface temperatures depends on the interplay of sea weathering and outgassing, which in turn depends on planetary carbon content, so that planets with lower carbon budgets are favored for temperate conditions. The habitability of planets such as found in the Trappist-1 system may be rooted in tidally driven tectonics.
The Colorado Plateau is a decaying landscape where erosion is decoupled from topography and most proposed tectonic drivers

NASA Astrophysics Data System (ADS)

Pederson, J. L.

2012-12-01

-to-apples across this landscape reveals a distinct central-Colorado Plateau bullseye of faster river incision that contrasts sharply with expectations based upon the patterns of energy expenditure and topography, but which matches modeled isostatic rebound from broad late Cenozoic exhumation of the Canyonlands district. Finally, recently proposed sources of late-Cenozoic mantle-driven support for topography at the south and west flanks of the plateau have low estimated rates of uplift, which are poorly constrained in terms of actual ongoing uplift versus just topographic support. Patterns of steepness and incision rate do not match the proposed mantle uplift, illustrating a poorly understood decoupling of erosion, topography, and mantle tectonics in the Colorado Plateau. Prime examples of this decoupling are the highly incised and steep Grand Canyon region where there are proposed sources of mantle uplift but contrastingly low rates of incision, versus the broadly exhumed central plateau that features much more rapid incision yet no mantle sources of uplift. Instead of active tectonics, bedrock resistance and possible drainage transients define geomorphic patterns in this landscape, while at broader wavelengths, the central plateau bullseye of rapid incision strongly matches the pattern of passive isostatic rebound.
How the continents deform: The evidence from tectonic geodesy

USGS Publications Warehouse

Thatcher, Wayne R.

2009-01-01

Space geodesy now provides quantitative maps of the surface velocity field within tectonically active regions, supplying constraints on the spatial distribution of deformation, the forces that drive it, and the brittle and ductile properties of continental lithosphere. Deformation is usefully described as relative motions among elastic blocks and is block-like because major faults are weaker than adjacent intact crust. Despite similarities, continental block kinematics differs from global plate tectonics: blocks are much smaller, typically ∼100–1000 km in size; departures from block rigidity are sometimes measurable; and blocks evolve over ∼1–10 Ma timescales, particularly near their often geometrically irregular boundaries. Quantitatively relating deformation to the forces that drive it requires simplifying assumptions about the strength distribution in the lithosphere. If brittle/elastic crust is strongest, interactions among blocks control the deformation. If ductile lithosphere is the stronger, its flow properties determine the surface deformation, and a continuum approach is preferable.
Venus magmatic and tectonic evolution

NASA Technical Reports Server (NTRS)

Phillips, R. J.; Hansen, V. L.

1993-01-01

Two years beyond the initial mapping by the Magellan spacecraft, hypotheses for the magmatic and tectonic evolution of Venus have become refined and focused. We present our view of these processes, attempting to synthesize aspects of a model for the tectonic and magmatic behavior of the planet. The ideas presented should be taken collectively as an hypothesis subject to further testing. The quintessence of our model is that shear and buoyancy forces in the upper boundary layer of mantle convection give rise to a spatially and temporally complex pattern of strain in a one-plate Venusian lithosphere and modulate the timing and occurrence of magmatism on a global basis.
Plate Tectonics on Earth-like Planets: Implications for Habitability

NASA Astrophysics Data System (ADS)

Noack, L.; Breuer, D.

2011-12-01

Plate tectonics has been suggested to be essential for life (see e.g. [1]) due to the replenishment of nutrients and its role in the stabilization of the atmosphere temperature through the carbon-silicate cycle. Whether plate tectonics can prevail on a planet should depend on several factors, e.g. planetary mass, age of the planet, water content (at the surface and in the interior), surface temperature, mantle rheology, density variations in the mantle due to partial melting, and life itself by promoting erosion processes and perhaps even the production of continental rock [2]. In the present study, we have investigated how planetary mass, internal heating, surface temperature and water content in the mantle would factor for the probability of plate tectonics to occur on a planet. We allow the viscosity to be a function of pressure [3], an effect mostly neglected in previous discussions of plate tectonics on exoplanets [4, 5]. With the pressure-dependence of viscosity allowed for, the lower mantle may become too viscous in massive planets for convection to occur. When varying the planetary mass between 0.1 and 10 Earth masses, we find a maximum for the likelihood of plate tectonics to occur for planetary masses around a few Earth masses. For these masses the convective stresses acting at the base of the lithosphere are strongest and may become larger than the lithosphere yield strength. The optimum planetary mass varies slightly depending on the parameter values used (e.g. wet or dry rheology; initial mantle temperature). However, the peak in likelihood of plate tectonics remains roughly in the range of one to five Earth masses for reasonable parameter choices. Internal heating has a similar effect on the occurrence of plate tectonics as the planetary mass, i.e. there is a peak in the probability of plate tectonics depending on the internal heating rate. This result suggests that a planet may evolve as a consequence of radioactive decay into and out of the plate
Erosion-tectonics feedbacks in shaping the landscape: An example from the Mekele Outlier (Tigray, Ethiopia)

NASA Astrophysics Data System (ADS)

Sembroni, Andrea; Molin, Paola; Dramis, Francesco; Faccenna, Claudio; Abebe, Bekele

2017-05-01

An outlier consists of an area of younger rocks surrounded by older ones. Its formation is mainly related to the erosion of surrounding rocks which causes the interruption of the original continuity of the rocks. Because of its origin, an outlier is an important witness of the paleogeography of a region and, therefore, essential to understand its topographic and geological evolution. The Mekele Outlier (N Ethiopia) is characterized by poorly incised Mesozoic marine sediments and dolerites (∼2000 m in elevation), surrounded by strongly eroded Precambrian and Paleozoic rocks and Tertiary volcanic deposits in a context of a mantle supported topography. In the past, studies about the Mekele outlier focused mainly in the mere description of the stratigraphic and tectonic settings without taking into account the feedback between surface and deep processes in shaping such peculiar feature. In this study we present the geological and geomorphometric analyses of the Mekele Outlier taking into account the general topographic features (slope map, swath profiles, local relief), the river network and the principal tectonic lineaments of the outlier. The results trace the evolution of the study area as related not only to the mere erosion of the surrounding rocks but to a complex interaction between surface and deep processes where the lithology played a crucial role.
Whole-mantle convection with tectonic plates preserves long-term global patterns of upper mantle geochemistry.

PubMed

Barry, T L; Davies, J H; Wolstencroft, M; Millar, I L; Zhao, Z; Jian, P; Safonova, I; Price, M

2017-05-12

The evolution of the planetary interior during plate tectonics is controlled by slow convection within the mantle. Global-scale geochemical differences across the upper mantle are known, but how they are preserved during convection has not been adequately explained. We demonstrate that the geographic patterns of chemical variations around the Earth's mantle endure as a direct result of whole-mantle convection within largely isolated cells defined by subducting plates. New 3D spherical numerical models embedded with the latest geological paleo-tectonic reconstructions and ground-truthed with new Hf-Nd isotope data, suggest that uppermost mantle at one location (e.g. under Indian Ocean) circulates down to the core-mantle boundary (CMB), but returns within ≥100 Myrs via large-scale convection to its approximate starting location. Modelled tracers pool at the CMB but do not disperse ubiquitously around it. Similarly, mantle beneath the Pacific does not spread to surrounding regions of the planet. The models fit global patterns of isotope data and may explain features such as the DUPAL anomaly and long-standing differences between Indian and Pacific Ocean crust. Indeed, the geochemical data suggests this mode of convection could have influenced the evolution of mantle composition since 550 Ma and potentially since the onset of plate tectonics.
Plate tectonics and planetary habitability: current status and future challenges.

PubMed

Korenaga, Jun

2012-07-01

Plate tectonics is one of the major factors affecting the potential habitability of a terrestrial planet. The physics of plate tectonics is, however, still far from being complete, leading to considerable uncertainty when discussing planetary habitability. Here, I summarize recent developments on the evolution of plate tectonics on Earth, which suggest a radically new view on Earth dynamics: convection in the mantle has been speeding up despite its secular cooling, and the operation of plate tectonics has been facilitated throughout Earth's history by the gradual subduction of water into an initially dry mantle. The role of plate tectonics in planetary habitability through its influence on atmospheric evolution is still difficult to quantify, and, to this end, it will be vital to better understand a coupled core-mantle-atmosphere system in the context of solar system evolution. © 2012 New York Academy of Sciences.
Geohistory analysis of the Santa Maria basin, California, and its relationship to tectonic evolution of the continental margin

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCrory, P.A.; Arends, R.G.; Ingle, J.C. Jr.

1991-02-01

The Santa Maria basin of central California is a geologically complex area located along the tectonically active California continental margin. The record of Cenozoic tectonism preserved in Santa Maria strata provides an opportunity to compare the evolution of the region with plate tectonic models for Cenozoic interactions along the margin. Geohistory analysis of Neogene Santa Maria basin strata provides important constraints for hypotheses of the tectonic evolution of the central California margin during its transition from a convergent to a transform plate boundary. Preliminary analyses suggest that the tectonic evolution of the Santa Maria area was dominated by coupling betweenmore » adjacent oceanic plates and the continental margin. This coupling is reflected in the timing of major hiatuses within the basin sedimentary sequence and margin subsidence and uplift which occurred during periods of tectonic plate adjustment. Stratigraphic evidence indicates that the Santa Maria basin originated on the continental shelf in early Miocene time. A component of margin subsidence is postulated to have been caused by cessation of spreading on adjacent offshore microplates approximately 19-18 ma. A sharp reduction in rate of tectonic subsidence in middle Miocene time, observed in the Santa Maria basin both onshore and offshore, was coeval with rotation of crustal blocks as major shearing shifts shoreward. Tectonic uplift of two eastern sites, offshore Point Arguello and near Point Sal, in the late Miocene may have been related to a change to transpressional motion between the Pacific and North American plates, as well as to rotation of the western Transverse Ranges in a restraining geometry.« less
47 CFR 79.109 - Activating accessibility features.

Code of Federal Regulations, 2014 CFR

2014-10-01

... ACCESSIBILITY OF VIDEO PROGRAMMING Apparatus § 79.109 Activating accessibility features. (a) Requirements... video programming transmitted in digital format simultaneously with sound, including apparatus designed to receive or display video programming transmitted in digital format using Internet protocol, with...
The many impacts of building mountain belts on plate tectonics and mantle flow

NASA Astrophysics Data System (ADS)

Yamato, Philippe; Husson, Laurent

2015-04-01

During the Cenozoic, the number of orogens on Earth increased. This observation readily indicates that in the same time, compression in the lithosphere became gradually more and more important. Such an increase of stresses in the lithosphere can impact on plate tectonics and mantle dynamics. We show that mountain belts at plate boundaries increasingly obstruct plate tectonics, slowing down and reorienting their motions. In turn, this changes the dynamic and kinematic surface conditions of the underlying flowing mantle. Ultimately, this modifies the pattern of mantle flow. This forcing could explain many first order features of Cenozoic plate tectonics and mantle flow. Among these, one can cite the compression of passive margins, the important variations in the rates of spreading at oceanic ridges, or the initiation of subduction, the onset of obduction, for the lithosphere. In the mantle, such change in boundary condition redesigns the pattern of mantle flow and, consequently, the oceanic lithosphere cooling. In order to test this hypothesis we first present thermo-mechanical numerical models of mantle convection above which a lithosphere rests. Our results show that when collision occurs, the mantle flow is highly modified, which leads to (i) increasing shear stresses below the lithosphere and (ii) to a modification of the convection style. In turn, the transition between a 'free' convection (mobile lid) and an 'upset' convection (stagnant -or sluggish- lid) highly impacts the dynamics of the lithosphere at the surface of the Earth. Thereby, on the basis of these models and a variety of real examples, we show that on the other side of a collision zone, passive margins become squeezed and can undergo compression, which may ultimately evolve into subduction or obduction. We also show that much further, due to the blocking of the lithosphere, spreading rates decrease at the ridge, a fact that may explain a variety of features such as the low magmatism of ultraslow
The Biggest Plates on Earth. Submarine Ring of Fire--Grades 5-6. Plate Tectonics.

ERIC Educational Resources Information Center

National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

This activity is designed to teach how tectonic plates move, what some consequences of this motion are, and how magnetic anomalies document the motion at spreading centers do. The activity provides learning objectives, a list of needed materials, key vocabulary words, background information, day-to-day procedures, internet connections, career…
Initiation of plate tectonics from post-magma ocean thermochemical convection

NASA Astrophysics Data System (ADS)

Foley, Bradford J.; Bercovici, David; Elkins-Tanton, Linda T.

2014-11-01

Leading theories for the presence of plate tectonics on Earth typically appeal to the role of present day conditions in promoting rheological weakening of the lithosphere. However, it is unknown whether the conditions of the early Earth were favorable for plate tectonics, or any form of subduction, and thus, how subduction begins is unclear. Using physical models based on grain-damage, a grainsize-feedback mechanism capable of producing plate-like mantle convection, we demonstrate that subduction was possible on the Hadean Earth (hereafter referred to as proto-subduction or proto-plate tectonics), that proto-subduction differed from modern day plate tectonics, and that it could initiate rapidly. Scaling laws for convection with grain-damage show that though either higher mantle temperatures or higher surface temperatures lead to slower plates, proto-subduction, with plate speeds of ≈1.75 cm/yr, can still be maintained in the Hadean, even with a CO2 rich primordial atmosphere. Furthermore, when the mantle potential temperature is high (e.g., above ≈2000 K), the mode of subduction switches to a "sluggish subduction" style, where downwellings are drip like and plate boundaries are diffuse. Finally, numerical models of post-magma ocean mantle convection demonstrate that proto-plate tectonics likely initiates within ˜100 Myr of magma ocean solidification, consistent with evidence from Hadean zircons. After the initiation of proto-subduction, non-plate-tectonic "sluggish subduction" prevails, giving way to modern style plate tectonics as both the mantle interior and climate cool. Hadean proto-subduction may hasten the onset of modern plate tectonics by drawing excess CO2 out of the atmosphere and cooling the climate.
Magmatism and underplating, a broadband seismic perspective on the Proterozoic tectonics of the Great Falls and Snowbird Tectonic Zones

NASA Astrophysics Data System (ADS)

Chen, Y.; Gu, Y. J.; Dokht, R.; Wang, R.

2017-12-01

The crustal and lithospheric structures beneath the Western Canada Sedimentary Basin (WCSB) and northern Montana contain vital records of the Precambrian tectonic development of Laurentia. In this study, we analyze the broadband seismic data recorded by the USArray and the most complete set of regional seismic networks to date near the WCSB. We adopt an integrated approach to investigate crustal structure and history, based primarily on P-to-S receiver functions but incorporate results from noise correlation functions, finite-frequency tomography and potential field measurements. In comparison with existing regional and global models, our stacked receiver functions show considerable improvements in the resolution of both Moho depth and Vp/Vs ratio. We identify major variations in Moho depth from the WCSB to the adjacent Cordillera. The Moho deepens steeply from 40 km in the Alberta basin to 50 km beneath the foothills, following Airy isostasy, but thermal buoyancy may be responsible for a flat, shallow ( 35 km) Moho to the west of the Rocky Mountain Trench. The Moho depth also increases sharply near the Snowbird Tectonic Zone (STZ), which is consistent with earlier findings from active-source data. Multiple lower crustal phases, a high velocity shallow mantle and elevated Vp/Vs ratios along the westernmost STZ jointly suggest major Proterozoic subduction and magmatism along this collisional boundary. In northern Montana, the Moho deepens along the Great Falls Tectonic Zone (GFTZ), a proposed Proterozoic suture between the Medicine Hat Block and Wyoming craton. This transition occurs near the Little Belt Mountain, which is located south of the Great Falls Shear Zone, an extensive northeast striking fault system characterized by strong potential field gradients. Similar to the STZ, our receiver functions offer new evidence for Proterozoic underplating in the vicinity of the GFTZ. In view of similar rock ages near the collisional boundaries in all parts of northern
An Update on Tectonics

NASA Astrophysics Data System (ADS)

Geissman, John W.; Faccenna, Claudio; Niemi, Nathan A.

2014-10-01

In February 1982, the first issue of Tectonics was published. In the editorial policy statement for the journal, founding editors John Dewey, Paul Tapponier, and Clark Burchfiel wrote, "The central theme of Tectonics is the mechanical and thermal evolution of the lithospheric crust and mantle and the way that this is reflected in cratons, basins and mountains from the broad regional scale to the fine scale." The editors further stated, "We expect that papers on these and related topics would emanate from a wide variety of earth science disciplines ranging from physical modeling to geological field observation." Finally, with the confidence from this incredible team of editors, they noted, "We are aiming for a very rapid review process, allowing a maximum of about 1 month between submission and notification to the author of acceptance or rejection."
Rapid biological speciation driven by tectonic evolution in New Zealand

NASA Astrophysics Data System (ADS)

Craw, Dave; Upton, Phaedra; Burridge, Christopher P.; Wallis, Graham P.; Waters, Jonathan M.

2016-02-01

Collisions between tectonic plates lead to the rise of new mountain ranges that can separate biological populations and ultimately result in new species. However, the identification of links between tectonic mountain-building and biological speciation is confounded by environmental and ecological factors. Thus, there are surprisingly few well-documented examples of direct tectonic controls on terrestrial biological speciation. Here we present examples from New Zealand, where the rapid evolution of 18 species of freshwater fishes has resulted from parallel tectonic landscape evolution. We use numerical models to reconstruct changes in the deep crustal structure and surface drainage catchments of the southern island of New Zealand over the past 25 million years. We show that the island and mountain topography evolved in six principal tectonic zones, which have distinct drainage catchments that separated fish populations. We use new and existing phylogenetic analyses of freshwater fish populations, based on over 1,000 specimens from more than 400 localities, to show that fish genomes can retain evidence of this tectonic landscape development, with a clear correlation between geologic age and extent of DNA sequence divergence. We conclude that landscape evolution has controlled on-going biological diversification over the past 25 million years.
Plate tectonics on the Earth triggered by plume-induced subduction initiation.

PubMed

Gerya, T V; Stern, R J; Baes, M; Sobolev, S V; Whattam, S A

2015-11-12

Scientific theories of how subduction and plate tectonics began on Earth--and what the tectonic structure of Earth was before this--remain enigmatic and contentious. Understanding viable scenarios for the onset of subduction and plate tectonics is hampered by the fact that subduction initiation processes must have been markedly different before the onset of global plate tectonics because most present-day subduction initiation mechanisms require acting plate forces and existing zones of lithospheric weakness, which are both consequences of plate tectonics. However, plume-induced subduction initiation could have started the first subduction zone without the help of plate tectonics. Here, we test this mechanism using high-resolution three-dimensional numerical thermomechanical modelling. We demonstrate that three key physical factors combine to trigger self-sustained subduction: (1) a strong, negatively buoyant oceanic lithosphere; (2) focused magmatic weakening and thinning of lithosphere above the plume; and (3) lubrication of the slab interface by hydrated crust. We also show that plume-induced subduction could only have been feasible in the hotter early Earth for old oceanic plates. In contrast, younger plates favoured episodic lithospheric drips rather than self-sustained subduction and global plate tectonics.
The Yilgarn Craton western Australia: A tectonic synthesis

NASA Technical Reports Server (NTRS)

Fripp, R. E. P.

1986-01-01

The Yilgarn Craton in Western Australia is one of the larger contiguous preserved Archaean crustal fragments, with an area of about 650,000 square kilometres. Of this, by area, about 70% is granitoid and 30% greenstone. The Craton is defined by the Darling Fault on its western margin, by Proterozoic deformation belts on its southern and northwestern margins, and by unconformable younger sediments on its eastern and northeastern margins. A regional geotectonic synthesis at a scale of 1:500,000 is being prepared. This is based largely upon the 1:250,000 scale mapping of the Geological Survey of Western Australia together with interpretation using geophysical data, mainly airborne magnetic surveys. On a regional basis the granitoids are classied as pre-, syn- and post-tectonic with respect to greenstone belt deformation. The post-tectonic granitoids yield Rb-Sr isochrons of about 2.6 b.y., close to Rb-Sr ages for the greenstones themselves which are up to about 2.8 b.y. old, although data for the latter is sparse. Contacts between earlier granitoids and greenstones which are not obscured by the post-tectonic granitoids are most commonly tectonic contacts, intensely deformed and with mylonitic fabrics. The general concensus however is that there is a pre-tectonic, pre-greenhouse sialic gneiss preserved in places. A discussion follows.
Impact of tectonic and volcanism on the Neogene evolution of isolated carbonate platforms (SW Indian Ocean)

NASA Astrophysics Data System (ADS)

Courgeon, S.; Jorry, S. J.; Jouet, G.; Camoin, G.; BouDagher-Fadel, M. K.; Bachèlery, P.; Caline, B.; Boichard, R.; Révillon, S.; Thomas, Y.; Thereau, E.; Guérin, C.

2017-06-01

Understanding the impact of tectonic activity and volcanism on long-term (i.e. millions years) evolution of shallow-water carbonate platforms represents a major issue for both industrial and academic perspectives. The southern central Mozambique Channel is characterized by a 100 km-long volcanic ridge hosting two guyots (the Hall and Jaguar banks) and a modern atoll (Bassas da India) fringed by a large terrace. Dredge sampling, geophysical acquisitions and submarines videos carried out during recent oceanographic cruises revealed that submarine flat-top seamounts correspond to karstified and drowned shallow-water carbonate platforms largely covered by volcanic material and structured by a dense network of normal faults. Microfacies and well-constrained stratigraphic data indicate that these carbonate platforms developed in shallow-water tropical environments during Miocene times and were characterized by biological assemblages dominated by corals, larger benthic foraminifera, red and green algae. The drowning of these isolated carbonate platforms is revealed by the deposition of outer shelf sediments during the Early Pliocene and seems closely linked to (1) volcanic activity typified by the establishment of wide lava flow complexes, and (2) to extensional tectonic deformation associated with high-offset normal faults dividing the flat-top seamounts into distinctive structural blocks. Explosive volcanic activity also affected platform carbonates and was responsible for the formation of crater(s) and the deposition of tuff layers including carbonate fragments. Shallow-water carbonate sedimentation resumed during Late Neogene time with the colonization of topographic highs inherited from tectonic deformation and volcanic accretion. Latest carbonate developments ultimately led to the formation of the Bassas da India modern atoll. The geological history of isolated carbonate platforms from the southern Mozambique Channel represents a new case illustrating the major
Applications of Morphochronology to the Active Tectonics of Tibet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryerson, F J; Tapponnier, P; Finkel, R C

2005-01-28

The Himalayas and the Tibetan Plateau were formed as a result of the collision of India and Asia, and provide an excellent opportunity to study the mechanical response of the continental lithosphere to tectonic stress. Geophysicists are divided in their views on the nature of this response advocating either (1) homogeneously distributed deformation with the lithosphere deforming as a fluid continuum or (2) deformation is highly localized with the lithosphere that deforms as a system of blocks. The resolution of this issue has broad implications for understanding the tectonic response of continental lithosphere in general. Homogeneous deformation is supported bymore » relatively low decadal, geodetic slip-rate estimates for the Altyn Tagh and Karakorum Faults. Localized deformation is supported by high millennial, geomorphic slip-rates constrained by both cosmogenic and radiocarbon dating on these faults. Based upon the agreement of rates determined by radiocarbon and cosmogenic dating, the overall linearity of offset versus age correlations, and on the plateau-wide correlation of landscape evolution and climate history, the disparity between geomorphic and geodetic slip-rate determinations is unlikely to be due to the effects of surface erosion on the cosmogenic age determinations. Similarly, based upon the consistency of slip-rates over various observation intervals, secular variations in slip-rate appear to persist no longer than 2000 years and are unlikely to provide reconciliation. Conversely, geodetic and geomorphic slip-rate estimates on the Kunlun fault, which does not have significant splays or associated thrust faults, are in good agreement, indicating that there is no fundamental reason why these complementary geodetic and geomorphic methods should disagree. Similarly, the geodetic and geomorphic estimates of shortening rates across the northeastern edge of the plateau are in reasonable agreement, and the geomorphic rates on individual thrust faults

Relation of MAGSAT and Gravity Anomalies to the Main Tectonic Provinces of South America. M.S. Thesis

NASA Technical Reports Server (NTRS)

Yuan, D. W.

1984-01-01

Magnetic anomalies of the South American continent are generally more positive and variable than the oceanic anomalies. There is better correlation between the magnetic anomalies and the major tectonic elements of the continents than between the anomalies and the main tectonic elements of the adjacent oceanic areas. Oceanic areas generally show no direct correlation to the magnetic anomalies. Precambrian continental shields are mainly more magnetic than continental basins and orogenic belts. Shields differ markedly from major aulacogens which are generally characterized by negative magnetic anomalies and positive gravity anomalies. The Andean orogenic belt shows rather poor correlation with the magnetic anomalies. The magnetic data exhibit instead prominent east-west trends, which although consistent with some tectonic features, may be related to processing noise derived from data reduction procedures to correct for external magnetic field effects. The pattern over the Andes is sufficiently distinct from the generally north trending magnetic anomalies occurring in the adjacent Pacific Ocean to separate effectively the leading edge of the South American Plate from the Nazea Plate. Eastern South America is characterized by magnetic anomalies which commonly extend across the continental margin into the Atlantic Ocean.
Tectonic tremor

USGS Publications Warehouse

Shelly, David R.

2016-01-01

Tectonic, non-volcanic tremor is a weak vibration of ground, which cannot be felt by humans but can be detected by sensitive seismometers. It is defined empirically as a low-amplitude, extended duration seismic signal associated with the deep portion (∼20–40 km depth) of some major faults. It is typically observed most clearly in the frequency range of 2–8 Hz and is depleted in energy at higher frequencies relative to regular earthquakes.
Training Classifiers with Shadow Features for Sensor-Based Human Activity Recognition.

PubMed

Fong, Simon; Song, Wei; Cho, Kyungeun; Wong, Raymond; Wong, Kelvin K L

2017-02-27

In this paper, a novel training/testing process for building/using a classification model based on human activity recognition (HAR) is proposed. Traditionally, HAR has been accomplished by a classifier that learns the activities of a person by training with skeletal data obtained from a motion sensor, such as Microsoft Kinect. These skeletal data are the spatial coordinates (x, y, z) of different parts of the human body. The numeric information forms time series, temporal records of movement sequences that can be used for training a classifier. In addition to the spatial features that describe current positions in the skeletal data, new features called 'shadow features' are used to improve the supervised learning efficacy of the classifier. Shadow features are inferred from the dynamics of body movements, and thereby modelling the underlying momentum of the performed activities. They provide extra dimensions of information for characterising activities in the classification process, and thereby significantly improve the classification accuracy. Two cases of HAR are tested using a classification model trained with shadow features: one is by using wearable sensor and the other is by a Kinect-based remote sensor. Our experiments can demonstrate the advantages of the new method, which will have an impact on human activity detection research.
Fault kinematics and tectonic stress in the seismically active Manyara Dodoma Rift segment in Central Tanzania Implications for the East African Rift

NASA Astrophysics Data System (ADS)

Macheyeki, Athanas S.; Delvaux, Damien; De Batist, Marc; Mruma, Abdulkarim

2008-07-01

The Eastern Branch of the East African Rift System is well known in Ethiopia (Main Ethiopian Rift) and Kenya (Kenya or Gregory Rift) and is usually considered to fade away southwards in the North Tanzanian Divergence, where it splits into the Eyasi, Manyara and Pangani segments. Further towards the south, rift structures are more weakly expressed and this area has not attracted much attention since the mapping and exploratory works of the 1950s. In November 4, 2002, an earthquake of magnitude Mb = 5.5 struck Dodoma, the capital city of Tanzania. Analysis of modern digital relief, seismological and geological data reveals that ongoing tectonic deformation is presently affecting a broad N-S trending belt, extending southward from the North Tanzanian Divergence to the region of Dodoma, forming the proposed "Manyara-Dodoma Rift segment". North of Arusha-Ngorongoro line, the rift is confined to a narrow belt (Natron graben in Tanzania) and south of it, it broadens into a wide deformation zone which includes both the Eyasi and Manyara grabens. The two-stage rifting model proposed for Kenya and North Tanzania also applies to the Manyara-Dodoma Rift segment. In a first stage, large, well-expressed topographic and volcanogenic structures were initiated in the Natron, Eyasi and Manyara grabens during the Late Miocene to Pliocene. From the Middle Pleistocene onwards, deformations related to the second rifting stage propagated southwards to the Dodoma region. These young structures have still limited morphological expressions compared to the structures formed during the first stage. However, they appear to be tectonically active as shown by the high concentration of moderate earthquakes into earthquake swarms, the distribution of He-bearing thermal springs, the morphological freshness of the fault scarps, and the presence of open surface fractures. Fault kinematic and paleostress analysis of geological fault data in basement rocks along the active fault lines show that recent
Progressive failure during the 1596 Keicho earthquakes on the Median Tectonic Line active fault zone, southwest Japan

NASA Astrophysics Data System (ADS)

Ikeda, M.; Toda, S.; Nishizaka, N.; Onishi, K.; Suzuki, S.

2015-12-01

Rupture patterns of a long fault system are controlled by spatial heterogeneity of fault strength and stress associated with geometrical characteristics and stress perturbation history. Mechanical process for sequential ruptures and multiple simultaneous ruptures, one of the characteristics of a long fault such as the North Anatolian fault, governs the size and frequency of large earthquakes. Here we introduce one of the cases in southwest Japan and explore what controls rupture initiation, sequential ruptures and fault branching on a long fault system. The Median Tectonic Line active fault zone　(hereinafter MTL) is the longest and most active fault in Japan. Based on historical accounts, a series of M ≥ 7 earthquakes occurred on at least a 300-km-long portion of the MTL in 1596. On September 1, the first event occurred on the Kawakami fault segment, in Central Shikoku, and the subsequent events occurred further west. Then on September 5, another rupture initiated from the Central to East Shikoku and then propagated toward the Rokko-Awaji fault zone to Kobe, a northern branch of the MTL, instead of the eastern main extent of the MTL. Another rupture eventually extended to near Kyoto. To reproduce this progressive failure, we applied two numerical models: one is a coulomb stress transfer; the other is a slip-tendency analysis under the tectonic stress. We found that Coulomb stress imparted from historical ruptures have triggered the subsequent ruptures nearby. However, stress transfer does not explain beginning of the sequence and rupture directivities. Instead, calculated slip-tendency values show highly variable along the MTL: high and low seismic potential in West and East Shikoku. The initiation point of the 1596 progressive failure locates near the boundary in the slip-tendency values. Furthermore, the slip-tendency on the Rokko-Awaji fault zone is far higher than that of the MTL in Wakayama, which may explain the rupture directivity toward Kobe-Kyoto.
Comparative analysis of geodynamic activity of the Caucasian and Eastern Mediterranean segments of the Alpine-Himalayan convergence zone

NASA Astrophysics Data System (ADS)

Chelidze, Tamaz; Eppelbaum, Lev

2013-04-01

activity in this region highlights the need for combined analysis of seismo-neotectonic signatures. For this purpose, this article presents the key features of the tectonic zonation of the Eastern Mediterranean. Map of derivatives of the gravity field retracked from the Geosat satellite and novel map of the Moho discontinuity illustrate the most important tectonic features of the region. The Post-Jurassic map of the deformation of surface leveling reflects the modern tectonic stage of Eastern Mediterranean evolution. The developed tectono-geophysical zonation map integrates the potential geophysical field analysis and seismic section utilization, as well as tectonic-structural, paleogeographical and facial analyses. Tectonically the map agrees with the earlier model of continental accretion (Ben-Avraham and Ginzburg, 1990). Overlaying the seismicity map of the Eastern Mediterranean tectonic region (for the period between 1900 and 2012) on the tectonic zonation chart reveals the key features of the seismo-neotectonic pattern of the Eastern Mediterranean. The results have important implications for tectonic-seismological analysis in this region (Eppelbaum and Katz, 2012). A difference in the geotectonic patterns makes interesting comparison of geodynamic activity and seismic hazard of the Caucasian and Eastern Mediterranean segments of the AHCZ.
CRUSTAL TECTONICS AND SEISMICITY OF THE MIDDLE EAST

NASA Astrophysics Data System (ADS)

Ghalib, H. A.; Gritto, R.; Sibol, M. S.; Herrmann, R. B.; Aleqabi, G. I.; Caron, P. F.; Wagner, R. A.; Ali, B. S.; Ali, A. A.

2009-12-01

The Arabian plate describes a geological entity and a dynamic system that has been in continuous interaction with the African plate to the west and south and the Eurasian plate to the north and east. The western and southern boundaries are distinguished by see floor spreading along the Gulf of Aden and Red Sea and transform faulting along the Dead Sea, whereas the northern and eastern boundaries are portrayed by compressional suture zones under thrusting the Turkish and Iranian plateaus. Despite this favorable juxtaposition of continental land masses and the plethora of national seismic networks in every country of the Middle East, the majority of published research on the Arabian plate and surrounding tectonic blocks still depends primarily on global seismographic stations and occasional local networks. Since 2005, we deployed a number of seismic stations, and more recently a five elements array, in close proximity to the northeastern boundary of the Arabian plate. The primary objective of the effort is to better understand the regional seismicity and seismotectonics of the Arabian plate and surrounding regions. To date over a terabyte of high quality 100 sps continuous three-component broadband data have been collected and being analyzed to derive models representative of the greater Middle East tectonic setting. This goal is, in part, achieved by estimating local and regional seismic velocity models using receiver function and surface wave dispersion analyses, and by using these models to obtain accurate hypocenter locations and event focal mechanisms. The resulting events distribution reveals a distinct picture of the interaction between the seismicity and tectonics of the region. The highest seismicity rate seems to be confined to the active northern section of the Zagros thrust zone, while it decreases towards the southern end, before the intensity increases again in the Bandar Abbas region. Spatial distribution of the events and stations provide thorough
Structural Mapping of Paterae and Mountains on Io: Implications for Crustal Stresses and Feature Evolution

NASA Astrophysics Data System (ADS)

Ahern, A.; Radebaugh, J.; Christiansen, E. H.; Harris, R. A.

2015-12-01

Paterae and mountains are some of the most distinguishing and well-distributed surface features on Io, and they reveal the role of tectonism in Io's crust. Paterae, similar to calderas, are volcano-tectonic collapse features that often have straight margins. Io's mountains are some of the highest in the solar system and contain linear features that reveal crustal stresses. Paterae and mountains are often found adjacent to one another, suggesting possible genetic relationships. We have produced twelve detailed regional structural maps from high-resolution images of relevant features, where available, as well as a global structural map from the Io Global Color Mosaic. The regional structural maps identify features such as fractures, lineations, folds, faults, and mass wasting scarps, which are then interpreted in the context of global and regional stress regimes. A total of 1048 structural lineations have been identified globally. Preliminary analyses of major thrust and normal fault orientations are dominantly 90° offset from each other, suggesting the maximum contractional stresses leading to large mountain formation are not a direct result of tidal extension. Rather, these results corroborate the model of volcanic loading of the crust and global shortening, leading to thrust faulting and uplift of coherent crustal blocks. Several paterae, such as Hi'iaka and Tohil, are found adjacent to mountains inside extensional basins where lava has migrated up normal faults to erupt onto patera floors. Over time, mass wasting and volcanic resurfacing can change mountains from young, steep, and angular peaks to older, gentler, and more rounded hills. Mass wasting scarps make up 53% of all features identified. The structural maps highlight the significant effect of mass wasting on Io's surface, the evolution of mountains through time, the role of tectonics in the formation of paterae, and the formation of mountains through global contraction due to volcanism.
Tertiary plate tectonics and high-pressure metamorphism in New Caledonia

USGS Publications Warehouse

Brothers, R.N.; Blake, M.C.

1973-01-01

The sialic basement of New Caledonia is a Permian-Jurassic greywacke sequence which was folded and metamorphosed to prehnite-pumpellyite or low-grade greenschist facies by the Late Jurassic. Succeeding Cretaceous-Eocene sediments unconformably overlie this basement and extend outwards onto oceanic crust. Tertiary tectonism occurred in three distinct phases. 1. (1) During the Late Eocene a nappe of peridotite was obducted onto southern New Caledonia from northeast to southwest, but without causing significant metamorphism in the underlying sialic rocks. 2. (2) Oligocene compressive thrust tectonics in the northern part of the island accompanied a major east-west subduction zone, at least 30 km wide, which is identified by an imbricate system of tectonically intruded melanges and by development of lawsonite-bearing assemblages in adjacent country rocks; this high-pressure mineralogy constituted a primary metamorphism for the Cretaceous-Eocene sedimentary pile, but was overprinted on the Mesozoic prehnite-pumpellyite metagreywackes. 3. (3) Post-Oligocene transcurrent faulting along a northwest-southeast line (the sillon) parallel to the west coast caused at least 150 km of dextral offset of the southwest frontal margin of the Eocene ultramafic nappe. At the present time, the tectonics of the southwest Pacific are related to a series of opposite facing subduction (Benioff) zones connected by transform faults extending from New Britain-Solomon Islands south through the New Hebrides to New Zealand and marking the boundary between the Australian and Pacific plates. Available geologic data from this region suggest that a similar geometry existed during the Tertiary and that the microcontinents of New Guinea, New Caledonia and New Zealand all lay along the former plate boundary which has since migrated north and east by a complex process of sea-floor spreading behind the active island arcs. ?? 1973.
Workshop on the Tectonic Evolution of Greenstone Belts

NASA Technical Reports Server (NTRS)

1986-01-01

The Workshop on the Tectonic Evolution of Greenstone Belts, which is part of the Universities Space Research Association, Lunar and Planetary Institute, of Houston, Texas, met there on Jan. 16-18, 1986. A number of plate tectonic hypotheses have been proposed to explain the origin of Archean and Phanerozoic greenstone/ophiolite terranes. These hypotheses are explored in the abstracts.
Holocene compression in the Acequión valley (Andes Precordillera, San Juan province, Argentina): Geomorphic, tectonic, and paleoseismic evidence

NASA Astrophysics Data System (ADS)

Audemard, M.; Franck, A.; Perucca, L.; Laura, P.; Pantano, Ana; Avila, Carlos R.; Onorato, M. Romina; Vargas, Horacio N.; Alvarado, Patricia; Viete, Hewart

2016-04-01

The Matagusanos-Maradona-Acequión Valley sits within the Andes Precordillera fold-thrust belt of western Argentina. It is an elongated topographic depression bounded by the roughly N-S trending Precordillera Central and Oriental in the San Juan Province. Moreover, it is not a piggy-back basin as we could have expected between two ranges belonging to a fold-thrust belt, but a very active tectonic corridor coinciding with a thick-skinned triangular zone, squeezed between two different tectonic domains. The two domains converge, where the Precordillera Oriental has been incorporated to the Sierras Pampeanas province, becoming the western leading edge of the west-verging broken foreland Sierras Pampeanas domain. This latter province has been in turn incorporated into the active deformation framework of the Andes back-arc at these latitudes as a result of enhanced coupling between the converging plates due to the subduction of the Juan Fernández ridge that flattens the Nazca slab under the South American continent. This study focuses on the neotectonics of the southern tip of this N-S elongated depression, known as Acequión (from the homonym river that crosses the area), between the Del Agua and Los Pozos rivers. This depression dies out against the transversely oriented Precordillera Sur, which exhibits a similar tectonic style as Precordillera Occidental and Central (east-verging fold-thrust belt). This contribution brings supporting evidence of the ongoing deformation during the Late Pleistocene and Holocene of the triangular zone bounded between the two leading and converging edges of Precordillera Central and Oriental thrust fronts, recorded in a multi-episodic lake sequence of the Acequión and Nikes rivers. The herein gathered evidence comprise Late Pleistocene-Holocene landforms of active thrusting, fault kinematics (micro-tectonic) data and outcrop-scale (meso-tectonic) faulting and folding of recent lake and alluvial sequences. In addition, seismically
Shale hydrocarbon reservoirs: some influences of tectonics and paleogeography during deposition: Chapter 2

USGS Publications Warehouse

Eoff, Jennifer D

2014-01-01

Fundamental to any of the processes that acted during deposition, however, was active tectonism. Basin type can often distinguish self-sourced shale plays from other types of hydrocarbon source rocks. The deposition of North American self-sourced shale was associated with the assembly and subsequent fragmentation of Pangea. Flooded foreland basins along collisional margins were the predominant depositional settings during the Paleozoic, whereas deposition in semirestricted basins was responsible along the rifted passive margin of the U.S. Gulf Coast during the Mesozoic. Tectonism during deposition of self-sourced shale, such as the Upper Jurassic Haynesville Formation, confined (re)cycling of organic materials to relatively closed systems, which promoted uncommonly thick accumulations of organic matter.
Tectonic and climatic control on evolution of rift lakes in the Central Kenya Rift, East Africa

NASA Astrophysics Data System (ADS)

Bergner, A. G. N.; Strecker, M. R.; Trauth, M. H.; Deino, A.; Gasse, F.; Blisniuk, P.; Dühnforth, M.

2009-12-01

The long-term histories of the neighboring Nakuru-Elmenteita and Naivasha lake basins in the Central Kenya Rift illustrate the relative importance of tectonic versus climatic effects on rift-lake evolution and the formation of disparate sedimentary environments. Although modern climate conditions in the Central Kenya Rift are very similar for these basins, hydrology and hydrochemistry of present-day lakes Nakuru, Elmenteita and Naivasha contrast dramatically due to tectonically controlled differences in basin geometries, catchment size, and fluvial processes. In this study, we use eighteen 14C and 40Ar/ 39Ar dated fluvio-lacustrine sedimentary sections to unravel the spatiotemporal evolution of the lake basins in response to tectonic and climatic influences. We reconstruct paleoclimatic and ecological trends recorded in these basins based on fossil diatom assemblages and geologic field mapping. Our study shows a tendency towards increasing alkalinity and shrinkage of water bodies in both lake basins during the last million years. Ongoing volcano-tectonic segmentation of the lake basins, as well as reorganization of upstream drainage networks have led to contrasting hydrologic regimes with adjacent alkaline and freshwater conditions. During extreme wet periods in the past, such as during the early Holocene climate optimum, lake levels were high and all basins evolved toward freshwater systems. During drier periods some of these lakes revert back to alkaline conditions, while others maintain freshwater characteristics. Our results have important implications for the use and interpretation of lake sediment as climate archives in tectonically active regions and emphasize the need to deconvolve lacustrine records with respect to tectonics versus climatic forcing mechanisms.
Soil radon profile of the Alhama de Murcia Fault: implications in tectonic segmentation

NASA Astrophysics Data System (ADS)

Bejar-Pizarro, M.; Perez Lopez, R.; Fernández Cortés, A.; Martínez-Díaz, J. J.; Staller, A.; Sánchez-Malo, A.; Sanz, E.; Cuezva, S.; Sánchez-Moral, S.

2017-12-01

Soil radon exhalation in active faults has been reported in several cases. Mobilization of radon gas in tectonic areas is related to CO2emission, acting as gas carrier from deeper fractured zones. Fluctuation of radon values can be correlated with earthquake occurrence. We have used the soil radon emission for characterizing different tectonic segment of the Alhama de Murcia Fault (FAM), one of the most active on-shore tectonic faults in Spain. The FAM is a NE-SW trending strike-slip fault with reverse component, 90 km long and it is capable to trigger M7 earthquakes, as far as several paleoseismic studies shown. The last destructive earthquake took place in 2011 and killed 9 people. Tectonic segmentation of this fault has been proposed, with a tectonic slip-rate close to 0.1 mm/yr from geomorphic evidence, whereas 0.5 mm/yr has been suggested from GPS geodetic measurements. We have developed a perpendicular profile for measuring the soil radon exhalation, in relationship with three principal segments of FAM from west to east: (1) Goñar-Lorca segment, (2) Lorca Totana segment and (3) Alhama segment. We have introduced radon passive detectors equipped with LR115 films in colluvium detritic deposits and at 0.8 m depth. Using detritic deposits affected by Quaternary fault movement we assure equal permeability conditions for radon transport. We used passive closed housings type DRF, with a filter that avoid thoron disturbance. Results show the largest values of radon emission close to the Quaternary surface ruptures (ca 3-5.5 kBq/m3). Furthermore, the Goñar segment exhibits the highest value (6 kBq/m3) although the Lorca segment shows an isotopic signal of 13dCO2 (-7.24‰) which indicates this is a mantle-rootled CO2, i.e. non-soil derived CO2 flux, likely related to CO2 produced by thermal decarbonation of underlying sedimentary rocks containing more marine carbonate minerals. These results are part of the combined Spanish projects GEIs-SUB (CGL2016- 78318-C2-1-R
Collapse Features

NASA Image and Video Library

2010-09-15

The depressions in this image from NASA Mars Odyssey likely formed due to both volcanic and tectonic forces. Tectonic forces likely account for some of the depressions, while collapse into lava tubes and lava flow erosion account for the remainder.
Tectonic control on the genesis of magmas in the New Hebrides arc (Vanuatu)

NASA Astrophysics Data System (ADS)

Beier, Christoph; Brandl, Philipp A.; Lima, Selma M.; Haase, Karsten M.

2018-07-01

reservoir. We interpret the occurrence of this fractional crystallisation end-member in a relatively thick island arc crust ( 30 km thickness) to result from isolated and relatively rapid ascent of melts, most likely through a complex system of dykes and sills that developed due to the tectonic positioning of Epi in a complex tectonic zone between a compressional environment in the north and an extensional setting in the south. We can show that the alignment of the cones largely depends on the local tectonic stress field at Epi that is especially influenced by a large dextral strike-slip zone, indicating that structural features have a significant impact on the location and composition of volcanic edifices.
Boninites: Characteristics and tectonic constraints, northeastern Appalachians

USGS Publications Warehouse

Kim, J.; Jacobi, R.D.

2002-01-01

Boninites are high Mg andesites that are thought to form in suprasubduction zone tectonic environments as primary melts from refractory mantle. Boninites provide a potential constraint on tectonic models for ancient terranes that contain boninites because the only unequivocal tectonic setting in which "modern" boninites have been recognized is a fore-arc setting. Tectonic models for "modern" boninite genesis include subduction initiation ("infant arc"), fore-arc spreading, and the forearc side of intra-arc rifting (spreading). These models can be differentiated by the relative age of the boninites and to a lesser degree, geochemistry. The distinctive geochemistry of boninites promotes their recognition in ancient terranes. As detailed in this report, several mafic terranes in the northeastern Appalachians contain boninites; these terranes were situated on both sides of Iapetus. The characteristics of these boninites can be used to constrain tectonic models of the evolution of the northeastern Appalachians. On the Laurentian side of Iapetus, "infant arc" boninites were not produced ubiquitously during the Cambrian subduction initiation, unless sampling problems or minimum age dates obscure a more widespread boninite "infant arc". The Cambrian subduction initiation on the Laurentian side was probably characterized by both "infant arc" boninitic arc construction (perhaps the >496 Ma Hawley Formation and the >488 Ma Betts Cove Ophiolite) and "normal" arc construction (Mt. Orford). This duality is consistent with the suggestion that the pre-collisional geometry of the Laurentian margin was complex. The Bay of Islands Complex and Thetford Mines ophiolite boninites are likely associated with forearc/intra-arc spreading during the protracted evolution of the Cambrian arc system. The relatively young boninites in the Bronson Hill Arc suggest that the Taconic continuous eastward subduction tectonic model is less tenable than other models. On the Gondwana side of Iapetus, the
Remote sensing revealed drainage anomalies and related tectonics of South India

NASA Astrophysics Data System (ADS)

Ramasamy, SM.; Kumanan, C. J.; Selvakumar, R.; Saravanavel, J.

2011-03-01

Drainages have characteristic pattern and life histories with youthful stage in hilly areas, mature stage in plains and old stage in the coastal zones. The deviations from their normal life histories, especially aberrations in their flow pattern in the form of various drainage anomalies have been inferred to be the indications of dominantly the Eustatic and Isostatic changes. This, especially after the advent of Earth Observing Satellites, has attracted the geoscientists from all over the world, for studying such drainage anomalies. In this connection, a study has been undertaken in parts of South India falling south of 14° south latitude to comprehensively map some drainage anomalies like deflected drainages, eyed drainages and compressed meanders and to evolve the tectonic scenario therefrom. The mapping of such mega drainage anomalies and the related lineaments/faults from the satellite digital data and the integration of such lineaments/faults with the overall lineament map of South India showed that the study area is marked by active N-S block faults and NE-SW sinistral and NW-SE dextral strike slip faults. Such an architecture of active tectonic grains indicates that the northerly directed compressive force which has originally drifted the Indian plate towards northerly is still active and deforming the Indian plate.
Tectonic Terminology: Some Proposed Changes

ERIC Educational Resources Information Center

Hill, Mason L.

1978-01-01

Plate tectonics concepts require a definition of fault, a new term to compliment epeirogeny, and a clarification of transform fault characteristics. This article makes proposals for these changes. (Author/MA)
Reducing risk where tectonic plates collide

USGS Publications Warehouse

Gomberg, Joan S.; Ludwig, Kristin A.

2017-06-19

Most of the world’s earthquakes, tsunamis, landslides, and volcanic eruptions are caused by the continuous motions of the many tectonic plates that make up the Earth’s outer shell. The most powerful of these natural hazards occur in subduction zones, where two plates collide and one is thrust beneath another. The U.S. Geological Survey’s (USGS) “Reducing Risk Where Tectonic Plates Collide—A USGS Plan to Advance Subduction Zone Science” is a blueprint for building the crucial scientific foundation needed to inform the policies and practices that can make our Nation more resilient to subduction zone-related hazards.

Mars: Lithospheric Flexure of the Tharsis Montes Volcanoes and the Evolutionary Relationship to Their Tectonic History

NASA Astrophysics Data System (ADS)

Chute, H.; Dombard, A. J.; Byrne, P. K.

2017-12-01

Lithospheric flexure associated with Arsia, Pavonis, and Ascraeus Montes has been previously studied to constrain the timeline and breadth of endogenic surface features surrounding these volcanoes. Here, we simulate the radial extent of two specific load-related features: annular graben and flank terraces. Detailed mapping of Ascraeus Mons (the youngest of the three volcanoes) showed a phase of compression of the edifice, forming the terraces and an annulus of graben immediately off the flanks, followed by a period of extension that formed additional graben superposed on the terraces on the lower flanks of the edifice. This transition from compression to extension on the lower flanks has been difficult to reconcile in mechanical models. We explore, with finite-element simulations, the effects of a thermal anomaly associated with an intrusive crustal underplate, which results in locally thinning the lithosphere (in contrast to past efforts that assumed a constant-thickness lithosphere). We find that it is primarily the horizontal extent of this thermal anomaly that governs how the lithosphere flexes under a volcano, as well as the transition from flank compression to a tight annulus of extensional stresses. Specifically, we propose that the structures on Ascraeus may be consistent with an early stage of volcanic growth accompanied by an underplate about the same width as the edifice that narrowed as volcanism waned, resulting in an inward migration of the extensional horizontal stresses from the surrounding plains onto the lower flanks. By linking the surface strains on the volcano with the volcano-tectonic evolution predicted by our flexure model, we can further constrain a more accurate timeline for the tectonic history of Ascraeus Mons. More broadly, because these tectonic structures are commonly observed, our results provide a general evolutionary model for large shield volcanoes on Mars.
The Foreign Language Feature Film and Language Teaching Activities.

ERIC Educational Resources Information Center

Chappell, Martin

1986-01-01

Analysis of foreign language films, featuring consideration of film sequence, image and film analysis, and literary adaptation, is an effective teaching activity with foreign language students. An example illustrates film analysis activities in a first-year French class. (CB)
Integrating EarthScope Data to Constrain the Long-Term Effects of Tectonism on Continental Lithosphere

NASA Astrophysics Data System (ADS)

Porter, R. C.; van der Lee, S.

2017-12-01

One of the most significant products of the EarthScope experiment has been the development of new seismic tomography models that take advantage of the consistent station design, regular 70-km station spacing, and wide aperture of the EarthScope Transportable Array (TA) network. These models have led to the discovery and interpretation of additional compositional, thermal, and density anomalies throughout the continental US, especially within tectonically stable regions. The goal of this work is use data from the EarthScope experiment to better elucidate the temporal relationship between tectonic activity and seismic velocities. To accomplish this, we compile several upper-mantle seismic velocity models from the Incorporated Research Institute for Seismology (IRIS) Earth Model Collaboration (EMC) and compare these to a tectonic age model we compiled using geochemical ages from the Interdisciplinary Earth Data Alliance: EarthChem Database. Results from this work confirms quantitatively that the time elapsed since the most recent tectonic event is a dominant influence on seismic velocities within the upper mantle across North America. To further understand this relationship, we apply mineral-physics models for peridotite to estimate upper-mantle temperatures for the continental US from tomographically imaged shear velocities. This work shows that the relationship between the estimated temperatures and the time elapsed since the most recent tectonic event is broadly consistent with plate cooling models, yet shows intriguing scatter. Ultimately, this work constrains the long-term thermal evolution of continental mantle lithosphere.
Drainage basin and topographic analysis of a tropical landscape: Insights into surface and tectonic processes in northern Borneo

NASA Astrophysics Data System (ADS)

Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Ramkumar, Mu.; Santosh, M.; Kumar, Shashi; Hassaan, Muhammad

2016-07-01

We investigated the recent landscape development of Borneo through geomorphic analysis of two large drainage basins (Rajang and Baram basins). The extraction of morphometric parameters utilizing digital terrain data in a GIS environment, focusing on hydrography (stream length-gradient index, ratio of valley floor width to valley height, and transverse topographic symmetry factor) and topography (local relief and relief anomaly), was carried out in order to elucidate processes governing drainage and landscape evolution. Anomalously high and low values of stream length-gradient indices of main tributary streams associated with faults and multiple knick-points along the channel profiles are linked to deformation events. The development of deeply incised V-shaped valleys show enhanced incision capability of streams in response to steepening of hillslope gradients following tectonic inputs. Deflection of streams and probable dynamic reorganization of the drainage system through stream capture processes as feedbacks to tectonic uplift and orographic effect are observed. Local relief and relief anomaly maps highlight the presence of preserved elevation-accordant relict portions of landscapes characterized by low amplitude relief, nested between ridgelines in regions of complex folding. Our results reveal dynamic geomorphic adjustment of the landscape due to perturbations in tectonic and climatic boundary conditions. The implication is that the landscape of north Borneo experienced a tectonic phase of rapid uplift after 5 Ma and undergoes active folding of the Rajang Group thrust belts in the present-day. Active shortening combined with high rates of denudation in Sarawak, demonstrates transience emphasized by the drainage system attempting to adjust to tectonic and climatic forcing.
Tectonic Evolution of the Jurassic Pacific Plate

NASA Astrophysics Data System (ADS)

Nakanishi, M.; Ishihara, T.

2015-12-01

We present the tectonic evolution of the Jurassic Pacific plate based on magnetic anomly lineations and abyssal hills. The Pacific plate is the largest oceanic plate on Earth. It was born as a microplate aroud the Izanagi-Farallon-Phoenix triple junction about 192 Ma, Early Jurassic [Nakanishi et al., 1992]. The size of the Pacific plate at 190 Ma was nearly half that of the present Easter or Juan Fernandez microplates in the East Pacific Rise [Martinez et at, 1991; Larson et al., 1992]. The plate boundary surrounding the Pacific plate from Early Jurassic to Early Cretaceous involved the four triple junctions among Pacific, Izanagi, Farallon, and Phoenix plates. The major tectonic events as the formation of oceanic plateaus and microplates during the period occurred in the vicinity of the triple junctions [e.g., Nakanishi and Winterer, 1998; Nakanishi et al., 1999], implying that the study of the triple junctions is indispensable for understanding the tectonic evolution of the Pacific plate. Previous studies indicate instability of the configuration of the triple junctions from Late Jurassic to Early Cretaceous (155-125 Ma). On the other hand, the age of the birth of the Pacific plate was determined assuming that all triple junctions had kept their configurations for about 30 m.y. [Nakanishi et al., 1992] because of insufficient information of the tectonic history of the Pacific plate before Late Jurassic.Increase in the bathymetric and geomagnetic data over the past two decades enables us to reveal the tectonic evolution of the Pacific-Izanagi-Farallon triple junction before Late Jurassic. Our detailed identication of magnetic anomaly lineations exposes magnetic bights before anomaly M25. We found the curved abyssal hills originated near the triple junction, which trend is parallel to magnetic anomaly lineations. These results imply that the configuration of the Pacific-Izanagi-Farallon triple junction had been RRR before Late Jurassic.
Tectonic Tremor analysis with the Taiwan Chelungpu-Fault Drilling Program (TCDP) downhole seismometer array

NASA Astrophysics Data System (ADS)

Lin, Y.; Hillers, G.; Ma, K.; Campillo, M.

2011-12-01

We study tectonic tremor activity in the Taichung area, Taiwan, analyzing continuous seismic records from 6 short-period sensors of the TCDP borehole array situated around 1 km depth. The low background noise level facilitates the detection of low-amplitude tectonic tremor and low-frequency earthquake (LFE) waveforms. We apply a hierarchical analysis to first detect transient amplitude increases, and to subsequently verify its tectonic origin, i.e. to associate it with tremor signals. The frequency content of tremor usually exceeds the background noise around 2-8 Hz; hence, in the first step, we use BHS1, BHS4 and BHS7 (top, center, bottom sensor) records to detect amplitude anomalies in this frequency range. We calculate the smoothed spectra of 30 second non-overlapping windows taken daily from 5 night time hours to avoid increased day time amplitudes associated with cultural activities. Amplitude detection is then performed on frequency dependent median values of 5 minute advancing, 10 minute long time windows, yielding a series of threshold dependent increased-energy spectra-envelopes, indicating teleseismic waveforms, potential tremor records, or other transients related to anthropogenic or natural sources. To verify the transients' tectonic origin, potential tremor waveforms detected by the amplitude method are manually picked in the time domain. We apply the Brown et al. (2008) LFE matched filter technique to three-component data from the 6 available sensors. Initial few-second templates are taken from the analyst-picked, minute-long segments, and correlated component-wise with 24-h data. Significantly increased similarity between templates and matched waveform segments is detected using the array-average 7-fold MAD measure. Harvested waveforms associated with this initial `weak' detection are stacked, and the thus created master templates are used in an iterative correlation procedure to arrive at robust LFE detections. The increased similarity of waveforms
Evolving Concepts and Teaching Approaches In Tectonics and Sedimentation.

ERIC Educational Resources Information Center

Graham, Stephan Alan

1983-01-01

Discusses five recent advances in sedimentary tectonics, noting how they are incorporated into college curricula. Advances discussed include basin type, tectonic setting, facies analysis (in conjunction with basin type/setting), stratigraphic analysis of reflection seismic data, and quantitative analysis of subsidence histories of sedimentary…
Unraveling tectonics and climate forcing in the late-Neogene exhumation history of South Alaska

NASA Astrophysics Data System (ADS)

Valla, Pierre; Champagnac, Jean-Daniel; Shuster, David; Herman, Frédéric; Giuditta Fellin, Maria

2015-04-01

The southern Alaska range presents an ideal setting to study the complex interactions between tectonics, climate and surface processes in landscape evolution. It exhibits active tectonics with the ongoing subduction/collision between Pacific and North America, and major active seismogenic reverse and strike-slip faults. The alpine landscape, rugged topography and the important ice-coverage at present reveal a strong glacial imprint associated with high erosion and sediment transport rates. Therefore, the relative importance of climatically-driven glacial erosion and tectonics for the observed late-exhumation history appears to be quite complex to decipher. Here, we first perform a formal inversion of an extensive bedrock thermochronological dataset from the literature to quantify the large-scale 20-Myr exhumation history over the entire southern Alaska. We show that almost half of the variability within the thermochronological record can be explained by modern annual precipitations spatial distribution, the residuals clearly evidencing localized exhumation along major tectonic structures of the frontal fold and thrust belt. Our results confirm high exhumation rates in the St Elias "syntaxis" and frontal zones for the last 0-2 Myr, where major ice fields and high precipitation rates likely sustained high exhumation rates; however the impact of late Cenozoic glaciations is difficult to constrain because of the low resolution on the exhumation history older than ~2 Myr. On the contrary, our inversion outcomes highlight that north of the Bagley Icefield the long-term exhumation has remained quite slow and continuous over the last ~20 Myr, with no late-stage signal of exhumation change since the onset of glaciations despite a clear glacial imprint on the landscape. We thus focus on the Granite Range (Wrangell-St Elias National Park, Alaska), an area presenting a strong glacial imprint but minor tectonic activity with only localized brittle deformation. We sampled four
Satellite Gravity Transforms Unmask Tectonic Pattern of Arabian-African Region

NASA Astrophysics Data System (ADS)

Eppelbaum, Lev; Katz, Youri

2017-04-01

belts: Alpine-Himalayan belt and Mesozoic terrane belt. The zone of active rifting of the Red Sea, Gulf of Aden and complex structure of Afar triangle as well as East African rift system are noticeably fixed. The boundary between the continental and crust in the SE part of the region (where occurs a transfer zone between the Gulf of Aden and Arabian Sea) is visibly detected. Application of informational approach (Eppelbaum and Khesin, 2012) enabled to reliably fix both continental and oceanic cratons and all belts. To south-east of the Horn of Africa the Arabian Sea Basin with oceanic crust is clearly distinguished. The East Arabian Craton (platform) as well as its framing are noticeably detected. Computation of entropy map from the satellite derived gravity field was earlier successfully tested by the authors in the Eastern Mediterranean (Eppelbaum and Katz, 2015a). Application of the adaptive form sliding window enables to receive the most reliable entropy estimations in conditions of complex field caused by superimposed influence of targets of different order. Obviously, computation of an entropial map by the same method for the region under study reproduces mainly deep tectonic units (elements) of the region. Complex pattern of entropial field in the SE part of the region reflects transfer from the Somalian Plate to Indian Plate (this area is characterized by the most mosaic pattern). This map nicely indicates position of the Mesozoic terrane belt and transition zone between the Victorian and Tanzanian plates. On the basis of advanced inverse method employment, the map indicating the most density contrast surface (discontinuity) in the upper mantle was developed. This map presents an intricate density-tectonic depth pattern of the region. Here such important tectonic features as the Afar Triple Junction and collision zone between the Arabian and Eurasian lithospheric plates are noticeably recognized. Besides this, we can note increasing of lithospheric thickness in
Inherited crustal features and tectonic blocks of the Transantarctic Mountains: An aeromagnetic perspective (Victoria Land, Antarctica)

NASA Astrophysics Data System (ADS)

Ferraccioli, F.; Bozzo, E.

1999-11-01

Aeromagnetic images covering a sector of the Transantarctic Mountains in Victoria Land as well as the adjacent Ross Sea are used to study possible relationships between tectonic blocks along the Cenozoic and Mesozoic West Antarctic rift shoulder and prerift features inherited mainly from the Paleozoic terranes involved in the Ross Orogen. The segmentation between the Prince Albert Mountains block and the Deep Freeze Range-Terra Nova Bay region is related to an inherited NW to NNW ice-covered boundary, which we name the "central Victoria Land boundary." It is interpreted to be the unexposed, southern continuation of the Ross age back arc Exiles thrust system recognized at the Pacific coast. The regional magnetic high to the west of the central Victoria Land boundary is attributed to Ross age calc-alkaline back arc intrusives forming the in-board Wilson "Terrane," thus shifting the previously interpreted Precambrian "shield" at least 100 km farther to the west. The high-frequency anomalies of the Prince Albert Mountains and beneath the Polar Plateau show that this region was extensively effected by Jurassic tholeiitic magmatism; NE to NNE trending magnetic lineations within this pattern could reflect Cretaceous and/or Cenozoic faulting. The western and eastern edges of the Deep Freeze Range block, which flanks the Mesozoic Rennick Graben, are marked by two NW magnetic lineaments following the Priestley and Campbell Faults. The Campbell Fault is interpreted to be the reactivated Wilson thrust fault zone and is the site of a major isotopic discontinuity in the basement. To the east of the Campbell Fault, much higher amplitude magnetic anomalies reveal mafic-ultramafic intrusives associated with the alkaline Meander Intrusive Group (Eocene-Miocene). These intrusives are likely genetically linked to the highly uplifted Southern Cross Mountains block. The NW-SE trends crossing the previously recognized ENE trending Polar 3 Anomaly offshore of the Southern Cross Mountains
Active Tectonics of the Far North Pacific Observed with GPS

NASA Astrophysics Data System (ADS)

Elliott, J.; Freymueller, J. T.; Jiang, Y.; Leonard, L. J.; Hyndman, R. D.; Mazzotti, S.

2017-12-01

The idea that the tectonics of the northeastern Pacific is defined by relatively discrete deformation along the boundary between the Pacific and North American plates has given way to a more complex picture of broad plate boundary zones and distributed deformation. This is due in large part to the Plate Boundary Observatory and several focused GPS studies, which have greatly increased the density of high-quality GPS data throughout the region. We will present an updated GPS velocity field in a consistent reference frame as well as a new, integrated block model that sheds light on regional tectonics and provides improved estimates of motion along faults and their potential seismic hazard. Crustal motions in southern Alaska are strongly influenced by the collision and flat-slab subduction of the Yakutat block along the central Gulf of Alaska margin. In the area nearest to the collisional front, small blocks showing evidence of internal deformation are required. East of the front, block motions show clockwise rotation into the Canadian Cordillera while west of the front there are counterclockwise rotations that extend along the Alaska forearc, suggesting crustal extrusion. Farther from the convergent margin, the crust appears to move as rigid blocks, with uniform motion over large areas. In western Alaska, block motions show a southwesterly rotation into the Bering Sea. Arctic Alaska displays southeasterly motions that gradually transition into easterly motion in Canada. Much of the southeastern Alaska panhandle and coastal British Columbia exhibit northwesterly motions. Although the relative plate motions are mainly accommodated along major faults systems, including the Fairweather-Queen Charlotte transform system, the St. Elias fold-and-thrust belt, the Denali-Totschunda system, and the Alaska-Aleutian subduction zone, a number of other faults accommodate lesser but still significant amounts of motion in the model. These faults include the eastern Denali/Duke River
Terrestrial source to deep-sea sink sediment budgets at high and low sea levels: Insights from tectonically active Southern California

USGS Publications Warehouse

Covault, J.A.; Romans, B.W.; Graham, S.A.; Fildani, A.; Hilley, G.E.

2011-01-01

Sediment routing from terrestrial source areas to the deep sea influences landscapes and seascapes and supply and filling of sedimentary basins. However, a comprehensive assessment of land-to-deep-sea sediment budgets over millennia with significant climate change is lacking. We provide source to sink sediment budgets using cosmogenic radionuclide-derived terrestrial denudation rates and submarine-fan deposition rates through sea-level fluctuations since oxygen isotope stage 3 (younger than 40 ka) in tectonically active, spatially restricted sediment-routing systems of Southern California. We show that source-area denudation and deep-sea deposition are balanced during a period of generally falling and low sea level (40-13 ka), but that deep-sea deposition exceeds terrestrial denudation during the subsequent period of rising and high sea level (younger than 13 ka). This additional supply of sediment is likely owed to enhanced dispersal of sediment across the shelf caused by seacliff erosion during postglacial shoreline transgression and initiation of submarine mass wasting. During periods of both low and high sea level, land and deep-sea sediment fluxes do not show orders of magnitude imbalances that might be expected in the wake of major sea-level changes. Thus, sediment-routing processes in a globally significant class of small, tectonically active systems might be fundamentally different from those of larger systems that drain entire orogens, in which sediment storage in coastal plains and wide continental shelves can exceed millions of years. Furthermore, in such small systems, depositional changes offshore can reflect onshore changes when viewed over time scales of several thousand years to more than 10 k.y. ?? 2011 Geological Society of America.
Geologic map of Mészáros revisited: Pioneering tectonic mapping of the Transdanubian Range in the early 1980s

NASA Astrophysics Data System (ADS)

Zámolyi, A.; Horváth, F.; Kovács, G.; Timár, G.; Székely, B.

2009-04-01

Rocks, even in tectonically active areas are very solid compared to the changes within the scientific theories that occured especially in Eastern Europe as the political landscape changed and the separation into socialist and capitalist countries started to fade. While in Western Europe, Wegener's mobilistic approach gained widespread acceptance in the 1960-ies, in the countries of Eastern Europe (partly due to political reasons) fixistic ideas were supported. Despite the fact that most important early concepts in Hungarian tectonics were born about a century ago as a results of exploration of the Lake Balaton and its surroundings conducted by Lajos Lóczy, initiatives to integrate various geodynamic observations were rare exceptions in the second half of the 20th century. The high priority of economic geologic prospection in order to find raw materials resulted in an enormous amount of observations. In the central Transdanubian Range (TR), hosting bauxite, coal and manganese deposits, extensive surveying was carried out according to fixistic tectonic concepts. Although the recognition of faults was of vital importance in mining, mapped faults were rarely integrated into a global geodynamic model. A pioneering approach was presented by Mészáros (1983), who compiled a 1: 100 000 scale structural and economic-geologic map of large parts of TR. The map focuses on the Bakony hills that are of key importance for the geodynamic understanding of the formation of PB. TR forms inselbergs with well preserved outcrops, which is rare in PB, thus allowing for direct measurements of fault striations and fault plane orientations. Prinz (1926) maintained the theory that the TR is a rigid block and named it Tisia block. An alternative to this approach was the monograph of Uhlig (1907) proposing mobilistic concepts. Csontos et al (1991) reviewed the evolution of neogene stress-fields in the Carpatho-Pannonian region observing microtectonic faults in TR. The authors conclude that
Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

NASA Astrophysics Data System (ADS)

Nishikawa, T.; Ide, S.

2017-07-01

Earthquake swarms are characterized by an increase in seismicity rate that lacks a distinguished main shock and does not obey Omori's law. At subduction zones, they are thought to be related to slow-slip events (SSEs) on the plate interface. Earthquake swarms in subduction zones can therefore be used as potential indicators of slow-slip events. However, the global distribution of earthquake swarms at subduction zones remains unclear. Here we present a method for detecting such earthquake sequences using the space-time epidemic-type aftershock-sequence model. We applied this method to seismicity (M ≥ 4.5) recorded in the Advanced National Seismic System catalog at subduction zones during the period of 1995-2009. We detected 453 swarms, which is about 6.7 times the number observed in a previous catalog. Foreshocks of some large earthquakes are also detected as earthquake swarms. In some subduction zones, such as at Ibaraki-Oki, Japan, swarm-like foreshocks and ordinary swarms repeatedly occur at the same location. Given that both foreshocks and swarms are related to SSEs on the plate interface, these regions may have experienced recurring SSEs. We then compare the swarm activity and tectonic properties of subduction zones, finding that swarm activity is positively correlated with curvature of the incoming plate before subduction. This result implies that swarm activity is controlled either by hydration of the incoming plate or by heterogeneity on the plate interface due to fracturing related to slab bending.
The origin of strike-slip tectonics in continental rifts

NASA Astrophysics Data System (ADS)

Ebinger, C. J.; Pagli, C.; Yun, S. H.; Keir, D.; Wang, H.

2016-12-01

Although continental rifts are zones of lithospheric extension, strike-slip tectonics is also accommodated within rifts and its origin remains controversial. Here we present a combined analysis of recent seismicity, InSAR and GPS derived strain maps to reveal that the plate motion in Afar is accommodated primarily by extensional tectonics in all rift arms and lacks evidences of regional scale bookshelf tectonics. However in the rifts of central Afar we identify crustal extension and normal faulting in the central part of the rifts but strike-slip earthquakes at the rift tips. We investigate if strike-slip can be the result of Coulomb stress changes induced by recent dyking but models do not explain these earthquakes. Instead we explain strike-slips as shearing at the tips of a broad zone of spreading where extension terminates against unstretched lithosphere. Our results demonstrate that plate spreading can develop both strike-slip and extensional tectonics in the same rifts.
Seismotectonic features of the African plate: the possible dislocation of a continent

NASA Astrophysics Data System (ADS)

Meghraoui, Mustapha

2014-05-01

The African continent is made of seismically active structures with active deformation in between main substratum shields considered as stable continental interiors. Seismically active regions are primarily located along rift zones, thrust and fold mountain belts, transform faults and volcanic fields. The active tectonic structures generated large and destructive earthquakes in the past with significant damage and economic losses in Africa. Although some regions of the continent show a low-level of seismic activity, several large earthquakes (with M > 7) have occurred in the past. The presence of major active faults that generate destructive earthquakes is among the most important geological and geophysical hazards for the continent. National and International scientific projects dealing with the seismic hazards assessment are increasing in seismically active regions in Africa. The UNESCO-SIDA/IGCP (Project 601 http://eost.u-strasbg.fr/~igcp601/) support the preparation and implementation of the "Seismotectonic Map of Africa". Therefore, new seismotectonic data with the regional analysis of earthquake hazards became necessary as a basis for a mitigation of the earthquake damage. A database in historical and instrumental seismicity, active tectonics, stress tensor distribution, earthquake geology and paleoseismology, active deformation, earthquake geodesy (GPS) and gravity, crustal structure studies, magnetic and structural segmentation, volcanic fields, collision tectonics and rifting processes is prepared to constrain the geodynamic evolution of the continent. Taking into account the geological, tectonic and geophysical characteristics, we define six seismotectonic provinces that characterize the crustal deformation. With the previously identified Somalia tectonic block, the seismotectonic and geophysical framework of the continent reveal the existence of the Cameroon volcanic line, the South African tectonic block with transform faulting and Cape folding system
Sedimentation and tectonics in the southern Bida Basin, Nigeria: depositional response to varying tectonic context

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braide, S.P.

1990-05-01

The Upper Cretaceous Bida basin of central Nigeria is sandwiched between the Precambrian schist belts of the Northern Nigerian massif and the West African craton. Of interest is the southern part of the basin, which developed in continental settings, because the facies architecture of the sedimentary fill suggests a close relation between sedimentation dynamics and basin margin tectonics. This relationship is significant to an understanding of the basin's origin, which has been controversial. A simple sag and rift origin has been suggested, and consequently dominated the negative thinking on the hydrocarbon prospects of the basin which were considered poor. Thismore » detailed study of the facies indicates rapid basin-wide changes from various alluvial fan facies through flood-basin and deltaic facies to lacustrine facies. Paleogeographic reconstruction suggests lacustrine environments were widespread and elongate. Lacustrine environments occurred at the basin's axis and close to the margins. This suggests the depocenter must have migrated during the basin's depositional history and subsided rapidly to accommodate the 3.5-km-thick sedimentary fill. Although distinguishing pull-apart basins from rift basins, based solely on sedimentologic grounds, may be difficult, the temporal migration of the depocenter, as well as the basin architecture of upward coarsening cyclicity, show a strong tectonic and structural overprint that suggests a tectonic framework for the Southern Bida basin similar in origin to a pull-apart basin.« less
The study of active tectonic based on hyperspectral remote sensing

NASA Astrophysics Data System (ADS)

Cui, J.; Zhang, S.; Zhang, J.; Shen, X.; Ding, R.; Xu, S.

2017-12-01

As of the latest technical methods, hyperspectral remote sensing technology has been widely used in each brach of the geosciences. However, it is still a blank for using the hyperspectral remote sensing to study the active structrure. Hyperspectral remote sensing, with high spectral resolution, continuous spectrum, continuous spatial data, low cost, etc, has great potentialities in the areas of stratum division and fault identification. Blind fault identification in plains and invisible fault discrimination in loess strata are the two hot problems in the current active fault research. Thus, the study of active fault based on the hyperspectral technology has great theoretical significance and practical value. Magnetic susceptibility (MS) records could reflect the rhythm alteration of the formation. Previous study shown that MS has correlation with spectral feature. In this study, the Emaokou section, located to the northwest of the town of Huairen, in Shanxi Province, has been chosen for invisible fault study. We collected data from the Emaokou section, including spectral data, hyperspectral image, MS data. MS models based on spectral features were established and applied to the UHD185 image for MS mapping. The results shown that MS map corresponded well to the loess sequences. It can recognize the stratum which can not identity by naked eyes. Invisible fault has been found in this section, which is useful for paleoearthquake analysis. The faults act as the conduit for migration of terrestrial gases, the fault zones, especially the structurally weak zones such as inrtersections or bends of fault, may has different material composition. We take Xiadian fault for study. Several samples cross-fault were collected and these samples were measured by ASD Field Spec 3 spectrometer. Spectral classification method has been used for spectral analysis, we found that the spectrum of the fault zone have four special spectral region(550-580nm, 600-700nm, 700-800nm and 800-900nm
Global tectonics and space geodesy

NASA Technical Reports Server (NTRS)

Gordon, Richard G.; Stein, Seth

1992-01-01

Much of the success of plate tectonics can be attributed to the near rigidity of tectonic plates and the availability of data that describe the rates and directions of motion across narrow plate boundaries of about 1 to 60 kilometers. Nonetheless, many plate boundaries in both continental and oceanic lithosphere are not narrow but are hundreds to thousands of kilometers wide. Wide plate boundary zones cover approximately 15 percent of earth's surface area. Space geodesy, which includes very long baseline radio interferometry, satellite laser ranging, and the global positioning system, provides the accurate long-distance measurements needed to estimate the present motion across and within wide plate boundary zones. Space geodetic data show that plate velocities averaged over years are remarkably similar to velocities avaraged over millions of years.
Global tectonics and space geodesy.

PubMed

Gordon, R G; Stein, S

1992-04-17

Much of the success of plate tectonics can be attributed to the near rigidity of tectonic plates and the availability of data that describe the rates and directions of motion across narrow plate boundaries \\m=~\\1 to 60 kilometers wide. Nonetheless, many plate boundaries in both continental and oceanic lithosphere are not narrow but are hundreds to thousands of kilometers wide. Wide plate boundary zones cover \\m=~\\15 percent of Earth's surface area. Space geodesy, which includes very long baseline radio interferometry, satellite laser ranging, and the global positioning system, is providing the accurate long-distance measurements needed to estimate the present motion across and within wide plate boundary zones. Space geodetic data show that plate velocities averaged over years are remarkably similar to velocities averaged over millions of years.

Plate tectonics, habitability and life

NASA Astrophysics Data System (ADS)

Spohn, Tilman; Breuer, Doris

2016-04-01

The role of plate tectonics in defining habitability of terrestrial planets is being increasingly discussed (e.g., Elkins-Tanton, 2015). Plate tectonics is a significantly evolved concept with a large variety of aspects. In the present context, cycling of material between near surface and mantle reservoirs is most important. But increased heat transport through mixing of cold lithosphere with the deep interior and formation of continental crust may also matter. An alternative mechanism of material cycling between these reservoirs is hot-spot volcanism combined with crust delamination. Hot-spot volcanism will transport volatiles to the atmosphere while delamination will mix crust, possibly altered by sedimentation and chemical reactions, with the mantle. The mechanism works as long as the stagnant lithosphere plate has not grown thicker than the crust and as long as volcanic material is added onto the crust. Thermal evolution studies suggest that the mechanism could work for the first 1-2 Ga of planetary evolution. The efficiency of the mechanism is limited by the ratio of extrusive to intrusive volcanism, which is thought to be less than 0.25. Plate tectonics would certainly have an advantage by working even for more evolved planets. A simple, most-used concept of habitability requires the thermodynamic stability of liquid water on the surface of a planet. Cycling of CO2between the atmosphere, oceans and interior through subduction and surface volcanism is an important element of the carbonate-silicate cycle, a thermostat feedback cycle that will keep the atmosphere from entering into a runaway greenhouse. Calculations for a model Earth lacking plate tectonics but degassing CO2, N, and H2O to form a surface ocean and a secondary atmosphere (Tosi et al, 2016) suggest that liquid water can be maintained on the surface for 4.5Ga. The model planet would then qualify as habitable. It is conceivable that the CO2 buffering capability of its ocean together with silicate
On the breakup of tectonic plates by polar wandering

NASA Technical Reports Server (NTRS)

Liu, H.-S.

1974-01-01

The equations for the stresses in a homogeneous shell of uniform thickness caused by a shift of the axis of rotation are derived. The magnitude of these stresses reaches a maximum value of the order of 10 to the 9th power dyn/sq cm, which is sufficient for explaining a tectonic breakup. In order to deduce the fracture pattern according to which the breakup of tectonic plates can be expected the theory of plastic deformation of shells is applied. The analysis of this pattern gives an explanation of the existing boundary systems of the major tectonic plates as described by Morgan (1968), LePichon (1968) and Isacks et al. (1968).
On volcanism and thermal tectonics on one-plate planets

NASA Technical Reports Server (NTRS)

Solomon, S. C.

1978-01-01

For planets with a single global lithospheric shell or 'plate', the thermal evolution of the interior affects the surface geologic history through volumetric expansion and the resultant thermal stress. Interior warming of such planets gives rise to extensional tectonics and a lithospheric stress system conductive to widespread volcanism. Interior cooling leads to compressional tectonics and lithospheric stresses that act to shut off surface volcanism. On the basis of observed surface tectonics, it is concluded that the age of peak planetary volume, the degree of early heating, and the age of youngest major volcanism on the one-plate terrestrial planets likely decrease in the order Mercury, Moon, Mars.
First results of an INGV project for the integrated analysis of the active tectonics in SW Sicily

NASA Astrophysics Data System (ADS)

Mattia, Mario; Giovanni, Barreca; Carla, Bottari; Valentina, Bruno; Pierfrancesco, Burrato; Fabrizio, Cultrera; Luigi, Dardanelli; Sofia, De Gregorio; Luigi, Ferranti; Laura, Guzzetta; Paolo, Madonia; Carmelo, Monaco; Claudia, Pipitone; Fabrizio, Pepe; Francesco, Guglielmino

2017-04-01

We present the first results of a project financed by the "Struttura Terremoti" of INGV to study the potential sources of earthquakes in south-western Sicily, including the area hit by the 1968 Belice earthquake sequence and the archaeological area of Selinunte, affected by two earthquakes in historical times. We adopt in this project a multi-disciplinary approach, with the goal of addressing the following points: 1) define the active tectonic framework of south-western Sicily, 2) investigate and characterize on-shore and off-shore faults, potential sources of damaging earthquakes, and 3) evaluate the current deformation rates. To do this, we collected a new set of geodetic (GPS and InSAR) and geochemical data, and performed geological and geomorphological surveys on-land in the area between Mazara, Castelvetrano and Selinunte. We also acquired high-resolution Sparker seismic profiles off-shore Sciacca. Geological and geomorphological surveys have been focused around the 10 km long Castelvetrano-Campobello di Mazara (CCM) lineament, where previous research (Barreca et al., 2014) showed geodetic and geoarchaeological evidence of recent deformation. In particular, a detailed survey of Quaternary coastal forms and deposits was performed, in order to reconstruct the sequence of uplifted paleoshorelines and to search for differential motions between adjacent coastal sectors spanning the CCM. Preliminary observations indicate that the footwall of the CCM hosts a larger number, and a more elevated position of paleo-shorelines suggestive of syntectonic uplift . A grid of about 200 km of high-resolution reflection seismic profiles was recorded along the continental shelf in the offshore of Sciacca. Profiles are mostly oriented in the WNW-ESE direction, with tie lines acquired in ENE-WSW direction. The acoustic source used during seismic prospecting was a 1 kJ Sparker power supply with a multi-tips Sparker array. Preliminary seismic data interpretation indicates that a
Western Aphrodite Terra, tectonics, geology, and line-of-sight gravity

NASA Technical Reports Server (NTRS)

Hays, John E.; Morgan, Paul

1992-01-01

Aphrodite Terra is the largest area of high-standing topography on Venus, and isostatic considerations strongly suggest that this high topography is supported at least in part by thickened crust. Previous studies of line-of-sight gravity data from the Pioneer Venus Orbiter indicate rapidly changing apparent depths of compensation across Aphrodite Terra. Magellan imaging data provide the first detailed images of this region, and we are mapping the region along Pioneer Venus orbit 440 to investigate whether the changing apparent depths of compensation correlate with changes in surficial tectonics. Preliminary mapping of geological features on Magellan images along the path of Pioneer Venus orbit 440 do not indicate a first-order correlation among surface features and changes in the apparent depth of compensation of line-of-sight gravity data. The apparent depth of compensation appears to be most variable in regions dominated by tessera, but not all areas of tessera have distinct gravity signatures. There is a weak correlation among areas in which impact craters are relatively common and areas in which the observed and predicted gravity anomalies are poorly correlated.
Training Classifiers with Shadow Features for Sensor-Based Human Activity Recognition

PubMed Central

Fong, Simon; Song, Wei; Cho, Kyungeun; Wong, Raymond; Wong, Kelvin K. L.

2017-01-01

In this paper, a novel training/testing process for building/using a classification model based on human activity recognition (HAR) is proposed. Traditionally, HAR has been accomplished by a classifier that learns the activities of a person by training with skeletal data obtained from a motion sensor, such as Microsoft Kinect. These skeletal data are the spatial coordinates (x, y, z) of different parts of the human body. The numeric information forms time series, temporal records of movement sequences that can be used for training a classifier. In addition to the spatial features that describe current positions in the skeletal data, new features called ‘shadow features’ are used to improve the supervised learning efficacy of the classifier. Shadow features are inferred from the dynamics of body movements, and thereby modelling the underlying momentum of the performed activities. They provide extra dimensions of information for characterising activities in the classification process, and thereby significantly improve the classification accuracy. Two cases of HAR are tested using a classification model trained with shadow features: one is by using wearable sensor and the other is by a Kinect-based remote sensor. Our experiments can demonstrate the advantages of the new method, which will have an impact on human activity detection research. PMID:28264470
Aeromagnetic anomalies reveal the link between magmatism and tectonics during the early formation of the Canary Islands.

PubMed

Blanco-Montenegro, Isabel; Montesinos, Fuensanta G; Arnoso, José

2018-01-08

The 3-D inverse modelling of a magnetic anomaly measured over the NW submarine edifice of the volcanic island of Gran Canaria revealed a large, reversely-magnetized, elongated structure following an ENE-WSW direction, which we interpreted as a sill-like magmatic intrusion emplaced during the submarine growth of this volcanic island, with a volume that could represent up to about 20% of the whole island. The elongated shape of this body suggests the existence of a major crustal fracture in the central part of the Canary Archipelago which would have favoured the rapid ascent and emplacement of magmas during a time span from 0.5 to 1.9 My during a reverse polarity chron of the Earth's magnetic field prior to 16 Ma. The agreement of our results with those of previous gravimetric, seismological and geodynamical studies strongly supports the idea that the genesis of the Canary Islands was conditioned by a strike-slip tectonic framework probably related to Atlas tectonic features in Africa. These results do not contradict the hotspot theory for the origin of the Canary magmatism, but they do introduce the essential role of regional crustal tectonics to explain where and how those magmas both reached the surface and built the volcanic edifices.
NREL Open House Features Energy Activities, Tours

Science.gov Websites

Open House Features Energy Activities, Tours For more information contact: e:mail: Public Affairs National Renewable Energy Laboratory (NREL) will open its doors 10 a.m. to 3 p.m., Saturday, July 24 for tours of its research facilities and interactive exhibits at the Visitors Center. The Open House
Plains Tectonics on Venus

NASA Technical Reports Server (NTRS)

Banerdt, W. B.; McGill, G. E.; Zuber, M. T.

1996-01-01

Tectonic deformation in the plains of Venus is pervasive, with virtually every area of the planet showing evidence for faulting or fracturing. This deformation can be classified into three general categories, defined by the intensity and areal extent of the surface deformation: distributed deformation, concentrated deformation, and local fracture patterns.
Quantitative analysis of the tectonic subsidence in the Potiguar Basin (NE Brazil)

NASA Astrophysics Data System (ADS)

Lopes, Juliana A. G.; de Castro, David L.; Bertotti, Giovanni

2018-06-01

The Potiguar Basin, located in the Brazilian Equatorial Margin, evolved from a complex rifting process implemented during the Atlantic Ocean opening in the Jurassic/Cretaceous. Different driving mechanisms were responsible for the onset of an aborted onshore rift and an offshore rift that initiated crustal rupture and the formation of a continental transform margin. Therefore, we applied the backstripping method to quantify the tectonic subsidence during the rift and post-rift phases of Potiguar Basin formation and to analyze the spatial variation of subsidence during the two successive and distinct tectonic events responsible for the basin evolution. The parameters required to apply this methodology were extracted from 2D seismic lines and exploratory well data. The tectonic subsidence curves present periods with moderate subsidence rates (up to 300 m/My), which correspond to the evolution of the onshore Potiguar Rift (∼141 to 128 Ma). From 128-118 Ma, the tectonic subsidence curves show no subsidence in the onshore Potiguar Basin, whereas subsidence occurred at high rates (over 300 m/My) in the offshore rift. The post-rift phase began ca. 118 Ma (Aptian), when the tectonic subsidence drastically slowed to less than 35 m/My, probably related to thermal relaxation. The tectonic subsidence rates in the various sectors of the Potiguar Rift, during the different rift phases, indicate that more intense faulting occurred in the southern portion of the onshore rift, along the main border faults, and in the southeastern portion of the offshore rift. During the post-rift phase, the tectonic subsidence rates increased from the onshore portion towards the offshore portion until the continental slope. The highest rates of post-rift subsidence (up to 35 m/My) are concentrated in the central region of the offshore portion and may be related to lithospheric processes related to the continental crust rupture and oceanic seafloor spreading. The variation in subsidence rates and
Evidence and dating of mid-Cretaceous tectonic activity in the San Rafael Swell, Emery County, Utah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eaton, J.G.; Kirkland, J.I.; Kauffman, E.G.

1990-04-01

Evidence of tectonic activity in the form of recycled conglomerates has been found in middle Cretaceous deposits on the western flank of the San Rafael Swell. These conglomerates, present in the upper part of the Dakota Formation and in the overlying basal Mancos Shale (Tununk Member), are separated by an earliest Turonian unconformity. The conglomerates appear to be derived from the Lower Cretaceous Buckhorn Conglomerate, or similar conglomerates, which were re-exposed by latest Cenomanian uplift. Coarse clastics provided to the nearshore facies of the Dakota Formation by coastal rivers are preserved as a coarsening upward sequence. Continued uplift eventually causedmore » a local marine regression by temporarily inhibiting the initial (latest Cenomanian) transgression of the Greenhorn Sea. In subaerially exposed environments pebbles and cobbles from the Buckhorn were distributed across the coastal floodplain by rivers. These clasts were reworked into a basal lag deposit when renewed transgression of the Greenhorn Sea occurred during the late early Turonian.« less
Late-Eburnean tectonic emplacement of Wayen syenite (Burkina Faso)

NASA Astrophysics Data System (ADS)

Seydoux Traoré, Abraham; Naba, Séta; Lompo, Martin

2010-05-01

The alkali plutonism of the Palaeoproterozoic domain of the West African craton remains very poorly studied. The rare data available are those from the Ninakri syenite and the alkali granites of central Côte d'Ivoire (Bonhomme, 1962; Morel and Alinat, 1993 ; Doumbia et al, 1998) and those of the alkali granites of central Burkina Faso (Wenmenga, 1986). All these studies focused on the petrographical characterization and the determination of the radiometric ages of these plutons. All ages were determined by the Rb/Sr and they vary between 1.8 Ga and 2.1 Ga. The span of emplacement ages suggests that the alkali plutonism of the Palaeoproterozoic of West Africa continued throughout the tectono-magmatic history of the craton. The purpose of the present study is to characterize the late eburnean tectonic processes using the structural data of the Wayen syenite which was dated at 2.1 Ga by Rb/Sr isochron by Vachette and Ouédraogo (1978) Map view and field relationships show that the Wayen syenite intrudes the metavolcanic and early plutonic rocks (tonalites, trondhjemites and granodiorites). The geochemical data show that the syenite has a peraluminous character (Peccerrilo and Taylor, 1976) and belongs to the S-type granitoids (Chappell and White, 1992). The structural data have been obtained by magnetic susceptibility (Km) measurements on 190 samples from 47 sampling stations. The values of susceptibility range between 253 µSI and 595,314 µSI. This means that we have both samples with ferromagnetic character (Km > 500 µSI) and paramagnetic character (Km ≤ 500 µSI). In the case of paramagnetism, the minerals bearing the magnetic susceptibility are ferriferous silicates (amphiboles and pyroxenes) whereas the in the ferromagnetic samples, it is magnetite. The microstructures of the syenite are mostly magmatic and very locally they show both high temperature solid state deformation features and relatively low temperature solid state conditions along narrow shear
ANALYSIS ON THE GROUND DESTROYED FEATURES AND TECTONIC STRESS FIELD OF THE 2008 WENCHUAN EARTHQUAKE AND OUR TREATING TACTICS

NASA Astrophysics Data System (ADS)

Guo, Y.; Wang, H.; Deng, Z.; You, H.

2009-12-01

To research the ground destroyed features and tectonic stress field of the 2008 Wenchuan Earthquake, we went the earthquake-hazard area, Hongkou Town in Dujiangyan City, Yingxiu Town in Wenchuan County, Bailu Town in Pengzhou City, Yinghua Town in Shifang City, Hanwang Town in Mianzhu City and Beichuan Cit early and late twice in 2008. The geological survey was made. Firstly, the ground destroyed features of the Wenchuan Earthquake around both Yingxiu - Beichuan Fracture and Guanxian - Jiangyou Fracture were analyzed. They mainly display as the ground crack ground, road steep slope, ground deformation, road rise high and deformation, road staggering and rupture, etc. Besides, the Wenchuan Earthquake resulted in the great deal of building collapse and lots of bridges damage even break down; It can be seen that the first floor of the building disappeared or damaged seriously; Some building still stood there although damaged by the earthquake; A few of building was damaged slightly and kept intact structure. Furthermore, the earthquake caused earth slide, mudflow and rolling stone, which lead to the building destroyed seriously, river blocked up, the life line engineering destroyed. Secondly, the phenomena of the ground destroy were analyzed preliminarily. The seismic intensity was determined based on the field investigation. The damaged situation of the construction was concluded. Based on the principle of structure geology and making use of the Stereographic projection, the stress field was analyzed according to the attitude, structural nature and relations among the fracture, fault scratch and joint fissure as well as the characteristics of ground deformation thirdly. The geodynamics of the 2008 Wenchuan Earthquake are probed into preliminarily. The main compressive stress (the maximum main stress) σ1 took Northeast by east direction, and the main tensile stress (the minimum main stress)σ3 took Northwest by north direction. The main fracture shows as the right
Alternative Conceptions of Plate Tectonics Held by Nonscience Undergraduates

ERIC Educational Resources Information Center

Clark, Scott K.; Libarkin, Julie C.; Kortz, Karen M.; Jordan, Sarah C.

2011-01-01

The theory of plate tectonics is the conceptual model through which most dynamic processes on Earth are understood. A solid understanding of the basic tenets of this theory is crucial in developing a scientifically literate public and future geoscientists. The size of plates and scale of tectonic processes are inherently unobservable,…
Interdisciplinary approach to exploit the tectonic memory in the continental crust of collisional belts.

NASA Astrophysics Data System (ADS)

Gosso, G.; Marotta, A. M.; Rebay, G.; Regorda, A.; Roda, M.; Spalla, M. I.; Zanoni, D.; Zucali, M.

2015-12-01

Collisional belts result by thoroughly competing thermo-mechanical disaggregation and coupling within both continental and oceanic lithospheric slices, during construction of tectono-metamorphic architectures. In multiply reworked metamorphics, tectonic units may be contoured nowadays on the base of coherent thermo-baric and structural time-sequences rather than simply relying on lithologic affinities. Sequences of equilibrium assemblages and related fabric imprints are an approach that appears as a more reliable procedure, that enables to define tectonic units as the volume of crustal slices that underwent corresponding variations during the dynamics of an active margin and takes into account a history of physical imprints. The dimensions of these tectonic units may have varied over time and must be reconstructed combining the tracers of structural and metamorphic changes of basement rocks, since such kind of tectono-metamorphic units (TMUs) is a realistic configuration of the discrete portions of orogenic crust that experienced a coherent sequence of metamorphic and textural variations. Their translational trajectories, and bulk shape changes during deformation, cannot simply be derived from the analysis of the geometries and kinematics of tectonic units, but are to be obtained by adding the reconstruction of quantitative P-T-d-t paths making full use of fossil mineral equilibria. The joint TMU field-and-laboratory definition is an investigation procedure that bears a distinct thermo-tectonic connotation, that, through modelling, offers the opportunity to test the physical compatibilities of plate-scale interconnected variables, such as density, viscosity, and heat transfer, with respect to what current interpretative geologic histories may imply. Comparison between predictions from numerical modelling and natural data obtained by this analytical approach can help to solve ambiguities on geodynamic significance of structural and thermal signatures, also as a
Geodetic, Geologic and Seismic Interdisciplinary Research of Tectonically Caused Movements in the Wider Area of the City of Zagreb

NASA Astrophysics Data System (ADS)

Dapo, A.; Pribicevic, B.; Herak, M.; Prelogovic, E.

2012-04-01

Since the last great earthquake in 1880 which shook the Zagreb area with IX° MCS, tectonic movements and models of numerous Zagreb faults have been the focal point of Croatian geologists, seismologists and in the last 15 years also geodetic scientists, who all have been working in the scope of their scientific branches on bringing the light to the tectonic mechanisms in the wider Zagreb area. Since it is tectonically very active area and being the Capitol city of the Croatia with very high population density it is of utmost importance to understand those mechanisms and to according to them find the best possible measures for protecting people and valuables. Best results are certainly going to be achieved through the interdisciplinary approach. That is why this paper presents first interdisciplinary results from geodetic, geologic and seismic researches and their contribution to the collective knowledge about tectonic movements in the wider area of the City of Zagreb.
A New Framework For The Evolution of Terrestrial Planets: Bi-stability, Stochastic Effects, and the Non-Uniqueness of Tectonic States

NASA Astrophysics Data System (ADS)

Weller, M. B.; Lenardic, A.

2017-12-01

Of all the Solar System bodies, the Earth is the only one for which significant observation and constraints are accessible such that they can be used to discriminate between competing models of Earth's tectonic evolution. Therefore, it is a natural tendency to use these observations to inform more general models of planetary evolution. Yet, our understating of Earth's evolution is far from complete. Geodynamic and geochemical evidence suggests that plate tectonics may not have operated on the early Earth, with both the timing of its onset and the length of its activity far from certain. In recent years, the potential of tectonic bi-stability (multiple stable, energetically allowed solutions) has been shown to be dynamically viable, both from analytical analysis and through numeric experiments in two and three dimensions. The indication is that multiple tectonic modes may operate on a single planetary body at different times within its temporal evolution. Further, there exists the potential that feedback mechanisms between the internal dynamics and surface processes (e.g., surface temperature changes driven by long term climate evolution), acting at different thermal evolution times, can cause terrestrial worlds to alternate between multiple tectonic states over giga-year timescales. Implied here is that terrestrial planets have the potential to migrate through tectonic regimes at similar `thermal evolutionary times' - points were planets have a similar bulk mantle temperature and energies -, but at very different `temporal times' - time since planetary formation. It can then be shown that identical planets at similar stages of their evolution may exhibit different tectonic regimes due to random fluctuations. A new framework of planetary evolution that moves toward probabilistic arguments based on general physical principals, as opposed to particular rheologies, and incorporates the potential of tectonic regime transitions and multiple tectonics states being viable
Tertiary tectonic in the Tehuantepec Isthmus, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopez, F.A.

1993-02-01

A microplate model in the basement was proposed according to photointerpretation of satellite imagery and supported with microtectonic studies in the Tehuantepec's Isthmus. The microplate is located in the northwestern part of the [open quotes]Sierra de Chiapas,[close quotes] and structurally has lineaments that correspond with sinestral wrench faults oriented northeast-southwest and dextral faults oriented northwest-southeast. In the front of the microplate, these faults are joined in an arc form. The microplate began its movement forward to the north in the middle Tertiary. This movement originated in a regional compressional stress that was younger to the north. The stress changed themore » orientation of the anticline axis from northwest-southeast to west-east. In its western limit, the stress produces a sinestral shear stress that built a rotational deformation in the [open quotes]Sierra Atravesada,[close quotes] and represents a superimposed tectonic block over an ancient (laramide) orogeny. This system has also produced other secondary transtensional effects oriented northwest-southeast, represented along the [open quotes]Depression Central del Istmo.[close quotes] The microplate has formed a tensional system opening the [open quotes]Superior, Inferior, and Mar Muerto[close quotes] lagoons. The microplate is strongly related with the relief, seismic activity, and the tectonics of the salt of the Tehuantepec's Isthmus.« less
Tectonics of icy satellites driven by melting and crystallization of water bodies inside their ice shells

NASA Astrophysics Data System (ADS)

Johnston, Stephanie Ann

Enceladus and Europa are icy satellites that currently support bodies of liquid water in the outer solar system Additionally, they show signs of being geologically active. Developing numerical models informed by observations of these icy satellites allows for the development of additional constraints and an improved understanding of the tectonics and evolution of icy satellites. The formation mechanisms for both chaos and ridges on Europa are thought to involve water as albedo changes observed in association with them imply the deposition of salt-rich water near these features. Ridges are the most ubiquitous feature on Europa and are described as central troughs flanked by two raised edifices, range in height from tens to hundreds of meters. Europan ridges can extend hundreds of km continuously along strike but are only about 2 km across. A model of a crystallizing dike--like water intrusion is able to match the overall morphology of ridges, and is consistent the long continuous strike. However, the intrusion of a large volume of water is required to match the most common heights of the ridges. Chaos on Europa is defined as a large area of disrupted ice that contain blocks of pre-existing material separated by a hummocky matrix. A proposed mechanism for the formation of Chaos is that a region of heterogeneous ice within the shell is melted and then recrystallizes. Comparing the model results with the geology of Thera Macula, a region where it has been proposed that Chaos is currently forming, suggests that additional processes may be needed to fully understand the development of Chaos. Water-rich plumes erupt from the south pole of Enceladus, suggesting the presence of a pressurized water reservoir. If a pressurized sea is located beneath the south polar terrain, its geometry and size in the ice shell would contribute to the stress state in the ice shell. The geometry and location of such an ocean, as well as the boundary conditions and thickness of an ice shell
Models of convection-driven tectonic plates - A comparison of methods and results

NASA Technical Reports Server (NTRS)

King, Scott D.; Gable, Carl W.; Weinstein, Stuart A.

1992-01-01

Recent numerical studies of convection in the earth's mantle have included various features of plate tectonics. This paper describes three methods of modeling plates: through material properties, through force balance, and through a thin power-law sheet approximation. The results obtained are compared using each method on a series of simple calculations. From these results, scaling relations between the different parameterizations are developed. While each method produces different degrees of deformation within the surface plate, the surface heat flux and average plate velocity agree to within a few percent. The main results are not dependent upon the plate modeling method and herefore are representative of the physical system modeled.

Tectonic wedging in the forearc basin - Accretionary prism transition, Lesser Antilles forearc

NASA Technical Reports Server (NTRS)

Torrini, Rudolph, Jr.; Speed, Robert C.

1989-01-01

This paper describes regional structure of the inner forearc of the southern Lesser Antilles, which contains an extensive 50-70 km wide inner forearc deformation belt (IFDB) developed above crystalline basement of the undeformed forearc basin (FAB), close to and perhaps above its probable subduction trace with Atlantic lithosphere. The IFDB is analyzed, with emphasis placed on five transects across the belt, using mainly migrated seismic sections and balanced model cross sections. The IFDB features and its evolution are discussed, with special attention given to the major structures divided by early and late stages of development, paleobathymetric history, event timing, displacement and strain, and alternative tectonic explanations.
The role of park conditions and features on park visitation and physical activity.

PubMed

Rung, Ariane L; Mowen, Andrew J; Broyles, Stephanie T; Gustat, Jeanette

2011-09-01

Neighborhood parks play an important role in promoting physical activity. We examined the effect of activity area, condition, and presence of supporting features on number of park users and park-based physical activity levels. 37 parks and 154 activity areas within parks were assessed during summer 2008 for their features and park-based physical activity. Outcomes included any park use, number of park users, mean and total energy expenditure. Independent variables included type and condition of activity area, supporting features, size of activity area, gender, and day of week. Multilevel models controlled for clustering of observations at activity area and park levels. Type of activity area was associated with number of park users, mean and total energy expenditure, with basketball courts having the highest number of users and total energy expenditure, and playgrounds having the highest mean energy expenditure. Condition of activity areas was positively associated with number of basketball court users and inversely associated with number of green space users and total green space energy expenditure. Various supporting features were both positively and negatively associated with each outcome. This study provides evidence regarding characteristics of parks that can contribute to achieving physical activity goals within recreational spaces.
Object activation in semantic memory from visual multimodal feature input.

PubMed

Kraut, Michael A; Kremen, Sarah; Moo, Lauren R; Segal, Jessica B; Calhoun, Vincent; Hart, John

2002-01-01

The human brain's representation of objects has been proposed to exist as a network of coactivated neural regions present in multiple cognitive systems. However, it is not known if there is a region specific to the process of activating an integrated object representation in semantic memory from multimodal feature stimuli (e.g., picture-word). A previous study using word-word feature pairs as stimulus input showed that the left thalamus is integrally involved in object activation (Kraut, Kremen, Segal, et al., this issue). In the present study, participants were presented picture-word pairs that are features of objects, with the task being to decide if together they "activated" an object not explicitly presented (e.g., picture of a candle and the word "icing" activate the internal representation of a "cake"). For picture-word pairs that combine to elicit an object, signal change was detected in the ventral temporo-occipital regions, pre-SMA, left primary somatomotor cortex, both caudate nuclei, and the dorsal thalami bilaterally. These findings suggest that the left thalamus is engaged for either picture or word stimuli, but the right thalamus appears to be involved when picture stimuli are also presented with words in semantic object activation tasks. The somatomotor signal changes are likely secondary to activation of the semantic object representations from multimodal visual stimuli.
Tectonic evolution of Western Ishtar Terra, Venus

NASA Astrophysics Data System (ADS)

Marinangeli, Lucia

1997-03-01

A detailed geological mapping based on Magellan data has been done in Western Ishtar Terra from 300-330 deg W to 65-75 deg N. The area studied comprises three main phisiografic provinces, Atropos Tessera, Akna Montes and North-Western Lakshmi Planum. The purposes of this study are (1) to recognize the tectonism of this area and investigate its type, direction, intensity, distribution and age relationships, (2) to define the link between the formation of the Akna mountain belt and the tectonic deformation in adjacent Tessera and Lakshmi Planum.
Is there uniformitarian or catastrophic tectonics on Venus?

NASA Technical Reports Server (NTRS)

Turcotte, Donald L.

1993-01-01

The distribution and modification of craters on Venus favors a near global, volcanic resurfacing event about 500 Myrs ago. Such an event indicates that the tectonic evolution of Venus was catastrophic rather than uniformitarian. The creation of a global, single-plate lithosphere on Venus about 500 Myrs ago can explain a variety of tectonic features on Venus that are not consistent with the thin lithosphere required by a uniformitarian hypothesis. A lithosphere on Venus that has thickened for 500 Myrs has a present thickness of about 300 km whereas steady-state heat loss from Venus requires a mean lithospheric thickness near 40 km. A thick lithosphere on Venus can support the high plateaus (elevations of 3-4 km) and mountain belts (up to 9 km) using the same isostatic compensation concepts applicable to the earth. If a thick lithosphere is thinned by a mantle plume, elevation is caused by thermal isostasy. The elevation due to the thinning of a 300 km thick lithosphere is about 3 km. Thus the domal elevation of Beta Regio can be explained by the same mechanism responsible for the elevation of the Hawaiian Swell. While the broad highland plateaus on Venus may be associated with thermal isostasy, the mountain belts in Ishtar Terra clearly cannot be. The high topography of Freyja Montes is almost certainly associated with underthrusting and the likely compensation mechanism is Airy isostasy associated with a thickened crust. With a density contrast delta, of 500 kg m(exp -3) an elevation of 9 km requires a crustal thickening of about 70 km. With a thick lithosphere there is no difficulty in supporting such a thick crust.
The Plate Tectonics Project

ERIC Educational Resources Information Center

Hein, Annamae J.

2011-01-01

The Plate Tectonics Project is a multiday, inquiry-based unit that facilitates students as self-motivated learners. Reliable Web sites are offered to assist with lessons, and a summative rubric is used to facilitate the holistic nature of the project. After each topic (parts of the Earth, continental drift, etc.) is covered, the students will…
Tectonic Evolution of Mars

NASA Technical Reports Server (NTRS)

Phillips, Roger J.

1992-01-01

The Final Technical Report on tectonic evolution of Mars is presented. Two papers and an abstract are included. Topics addressed include: scientific rationale and requirements for a global seismic network on Mars, permanent uplift in magmatic systems with application to the Tharsis Region of Mars, and the geophysical signal of the Martian global dichotomy.
Seismic hazard assessment of Syria using seismicity, DEM, slope, active tectonic and GIS

NASA Astrophysics Data System (ADS)

Ahmad, Raed; Adris, Ahmad; Singh, Ramesh

2016-07-01

In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of seismic hazard areas in Syria. The present study is the first time effort to create seismic hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and active tectonic maps. Many important factors for evaluation of seismic hazard were identified and corresponding thematic data layers (past earthquake epicenters, active faults, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of seismic hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final seismic hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of seismic hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic seismic hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of seismic hazard map which is found to be very realistic.
Geology Field Camp at Southern Illinois University: Six weeks exploring four tectonic regimes

NASA Astrophysics Data System (ADS)

Friedman, S. A.; Conder, J. A.; Ferre, E. C.; Heij, G.

2013-12-01

Field Geology is typically the capstone course for an undergraduate Bachelor of Science degree in Geology. This type of course brings together the varied sub-disciplines and course topics students encounter in their undergraduate experience, and puts these in context of active Earth processes. At the same time, a significant fraction of Geology departments have dropped field geology from their offerings and students must choose from those programs still offering the course. Southern Illinois University has offered field geology for over 40 years, stationed in and around southwestern Montana. This field camp offers experiences with four distinct tectonic settings: thick-skin contractional, thin-skin contractional, extensional, and anorogenic. The most challenging projects of the course involve mapping and interpreting Laramide and Sevier compressionally deformed areas. The major difference between the two types of deformation is that Laramide ('thick-skinned') tectonics encompasses the mid-crust in deformation while Sevier ('thin-skinned') deformation is limited to the uppermost portion of the crust. This difference results in markedly different fold styles and other deformational structures encountered, requiring different approaches to understanding and constructing the deformational histories of the regions. Extensional tectonics are explored with a paleoseismology project at Hebgen Lake, in Grand Teton National Park where the students typically spend two days, and at the Bitterroot Shear Zone - the edge of a metamorphic core complex along the eastern boundary of the Idaho batholith. While recent work from EarthScope and elsewhere casts doubt on Yellowstone as a mantle plume, Yellowstone remains the classic example of a continental hotspot. During visits through the park, students distinguish between the recent volcanics and hydrothermal activity of Yellowstone and the nearby Eocene Absaroka volcanics. Expanding on the story of the Yellowstone hotspot, a visit is
MEVTV Workshop on Early Tectonic and Volcanic Evolution of Mars

NASA Technical Reports Server (NTRS)

Frey, H. (Editor)

1988-01-01

Although not ignored, the problems of the early tectonic and volcanic evolution of Mars have generally received less attention than those later in the evolution of the planet. Specifically, much attention was devoted to the evolution of the Tharsis region of Mars and to the planet itself at the time following the establishment of this major tectonic and volcanic province. By contrast, little attention was directed at fundamental questions, such as the conditions that led to the development of Tharsis and the cause of the basic fundamental dichotomy of the Martian crust. It was to address these and related questions of the earliest evolution of Mars that a workshop was organized under the auspices of the Mars: Evolution of Volcanism, Tectonism, and Volatiles (MEVTV) Program. Four sessions were held: crustal dichotomy; crustal differentiation/volcanism; Tharsis, Elysium, and Valles Marineris; and ridges and fault tectonics.
Phanerozoic tectonic evolution of the Circum-North Pacific

USGS Publications Warehouse

Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Norton, Ian O.; Khanchuk, Alexander I.; Stone, David B.; Scotese, Christopher R.; Scholl, David W.; Fujita, Kazuya

2000-01-01

The Phanerozoic tectonic evolution of the Circum-North Pacific is recorded mainly in the orogenic collages of the Circum-North Pacific mountain belts that separate the North Pacific from the eastern part of the North Asian Craton and the western part of the North American Craton. These collages consist of tectonostratigraphic terranes that are composed of fragments of igneous arcs, accretionary-wedge and subduction-zone complexes, passive continental margins, and cratons; they are overlapped by continental-margin-arc and sedimentary-basin assemblages. The geologic history of the terranes and overlap assemblages is highly complex because of postaccretionary dismemberment and translation during strike-slip faulting that occurred subparallel to continental margins.We analyze the complex tectonics of this region by the following steps. (1) We assign tectonic environments for the orogenic collages from regional compilation and synthesis of stratigraphic and faunal data. The types of tectonic environments include cratonal, passive continental margin, metamorphosed continental margin, continental-margin arc, island arc, oceanic crust, seamount, ophiolite, accretionary wedge, subduction zone, turbidite basin, and metamorphic. (2) We make correlations between terranes. (3) We group coeval terranes into a single tectonic origin, for example, a single island arc or subduction zone. (4) We group igneous-arc and subduction- zone terranes, which are interpreted as being tectonically linked, into coeval, curvilinear arc/subduction-zone complexes. (5) We interpret the original positions of terranes, using geologic, faunal, and paleomagnetic data. (6) We construct the paths of tectonic migration. Six processes overlapping in time were responsible for most of the complexities of the collage of terranes and overlap assemblages around the Circum-North Pacific, as follows. (1) During the Late Proterozoic, Late Devonian, and Early Carboniferous, major periods of rifting occurred along
The Rae craton of Laurentia/Nuna: a tectonically unique entity providing critical insights into the concept of Precambrian supercontinental cyclicity

NASA Astrophysics Data System (ADS)

Bethune, K. M.

2015-12-01

Forming the nucleus of Laurentia/Nuna, the Rae craton contains rocks and structures ranging from Paleo/Mesoarchean to Mesoproterozoic in age and has long been known for a high degree of tectonic complexity. Recent work strongly supports the notion that the Rae developed independently from the Hearne; however, while the Hearne appears to have been affiliated with the Superior craton and related blocks of 'Superia', the genealogy of Rae is far less clear. A diagnostic feature of the Rae, setting it apart from both Hearne and Slave, is the high degree of late Neoarchean to early Paleoproterozoic reworking. Indeed, following a widespread 2.62-2.58 Ga granite bloom, the margins of Rae were subjected to seemingly continuous tectonism, with 2.55-2.50 Ga MacQuoid orogenesis in the east superseded by 2.50 to 2.28 Ga Arrowsmith orogenesis in the west. A recent wide-ranging survey of Hf isotopic ratios in detrital and magmatic zircons across Rae has demonstrated significant juvenile, subduction-related crustal production in this period. Following break-up at ca. 2.1 Ga, the Rae later became a tectonic aggregation point as the western and eastern margins transitioned back to convergent plate boundaries (Thelon-Taltson and Snowbird orogens) marking onset of the 2.0-1.8 Ga assembly of Nuna. The distinctive features of Rae, including orogenic imprints of MacQuoid and Arrowsmith vintage have now been identified in about two dozen cratonic blocks world-wide, substantiating the idea that the Rae cratonic family spawned from an independent earliest Paleoproterozoic landmass before its incorportation in Nuna. While critical tests remain to be made, including more reliable ground-truthing of proposed global correlations, these relationships strongly support the notion of supercontinental cyclicity in the Precambrian, including the Archean. They also challenge the idea of a globally quiescent period in the early Paleoproterozoic (2.45-2.2 Ga) in which plate tectonics slowed or shut down.
Investigation of Tectonic Boundaries in Taiwan Obtained with a Hierarchical Clustering of Dense GNSS Data

NASA Astrophysics Data System (ADS)

Takahashi, A.; Hashimoto, M.; Hu, J. C.; Fukahata, Y.

2017-12-01

Taiwan Island is composed of many geological structures. The main tectonic feature is the collision of the Luzon volcanic arc with the Eurasian continent, which propagates westward and generates complicated crustal deformation. One way to model crustal deformation is to divide Taiwan island into man rigid blocks that moves relatively each other along the boundaries (deformation zones) of the blocks. Since earthquakes tend to occur in the deformation zones, identification of such tectonic boundaries is important. So far, many tectonic boundaries have been proposed on the basis of geology, geomorphology, seismology and geodesy. However, which is the most significant boundary depends on disciplines and there is no way to objectively classify them. Here, we introduce an objective method to identify significant tectonic boundaries with a hierarchical representation proposed by Simpson et al. [2012].We apply a hierarchical agglomerative clustering algorithm to dense GNSS horizontal velocity data in Taiwan. One of the significant merits of the hierarchical representation of the clustering results is that we can consistently explore crustal structures from larger to smaller scales. This is because a higher hierarchy corresponds to a larger crustal structure, and a lower hierarchy corresponds to a smaller crustal structure. Relative motion between clusters can be obtained from this analysis.The first major boundary is identified along the eastern margin of the Longitudinal Valley, which corresponds to the separation of the Philippine Sea plate and the Eurasian continental margin. The second major boundary appears along the Chaochou fault and the Chishan fault in southwestern Taiwan. The third major boundary appears along the eastern margin of the coastal plane. The identified major clusters can be divided into several smaller blocks without losing consistency with geological boundaries. For example, the Fengshun fault, concealed beneath thick sediment layers, is identified
Relief Evolution in Tectonically Active Mountain Ranges

NASA Technical Reports Server (NTRS)

Whipple, Kelin X.

2004-01-01

The overall aims of this 3-yr project, as originally proposed were to: (1) investigate quantitatively the roles of fluvial and glacial erosion in the evolution of relief in mountainous regions, and (2) test rigorously the quality and accuracy of SRTM topographic data in areas of rugged relief - both the most challenging and of greatest interest to geomorphic, neotectonic, and hazards applications. Natural laboratories in both the western US and the Southern Alps of New Zealand were identified as most promising. The project has been both successful and productive, despite the fact that no SRTM data for our primary field sites in New Zealand were released on the time frame of the work effort. Given the delayed release of SRTM data, we pursued the scientific questions of the roles of fluvial and, especially, glacial erosion in the evolution of relief in mountainous regions using available digital elevation models (DEMs) for the Southern Alps of New Zealand (available at both 25m and 50m pixel sizes), and USGS 10m and 30m DEMs within the Western US. As emphasized in the original proposal, we chose the emphasis on the role of glacial modification of topographic relief because there has been little quantitative investigation of glacial erosion processes at landscape scale. This is particularly surprising considering the dramatic sculpting of most mid- and high-latitude mountain ranges, the prodigious quantities of glacially-derived sediment in terrestrial and marine basins, and the current cross-disciplinary interest in the role of denudational processes in orogenesis and the evolution of topography in general. Moreover, the evolution of glaciated landscapes is not only a fundamental problem in geomorphology in its own right, but also is at the heart of the debate over Late Cenozoic linkages between climate and tectonics.
SmallWorld Behavior of the Worldwide Active Volcanoes Network: Preliminary Results

NASA Astrophysics Data System (ADS)

Spata, A.; Bonforte, A.; Nunnari, G.; Puglisi, G.

2009-12-01

We propose a preliminary complex networks based approach in order to model and characterize volcanoes activity correlation observed on a planetary scale over the last two thousand years. Worldwide volcanic activity is in fact related to the general plate tectonics that locally drives the faults activity, that in turn controls the magma upraise beneath the volcanoes. To find correlations among different volcanoes could indicate a common underlying mechanism driving their activity and could help us interpreting the deeper common dynamics controlling their unrest. All the first evidences found testing the procedure, suggest the suitability of this analysis to investigate global volcanism related to plate tectonics. The first correlations found, in fact, indicate that an underlying common large-scale dynamics seems to drive volcanic activity at least around the Pacific plate, where it collides and subduces beneath American, Eurasian and Australian plates. From this still preliminary analysis, also more complex relationships among volcanoes lying on different tectonic margins have been found, suggesting some more complex interrelationships between different plates. The understanding of eventually detected correlations could be also used to further implement warning systems, relating the unrest probabilities of a specific volcano also to the ongoing activity to the correlated ones. Our preliminary results suggest that, as for other many physical and biological systems, an underlying organizing principle of planetary volcanoes activity might exist and it could be a small-world principle. In fact we found that, from a topological perspective, volcanoes correlations are characterized by the typical features of small-world network: a high clustering coefficient and a low characteristic path length. These features confirm that global volcanoes activity is characterized by both short and long-range correlations. We stress here the fact that numerical simulation carried out in
Thick-skinned tectonics closing the Rifian Corridor

NASA Astrophysics Data System (ADS)

Capella, Walter; Matenco, Liviu; Dmitrieva, Evelina; Roest, Wilmer M. J.; Hessels, Suzanne; Hssain, Mohamed; Chakor-Alami, Abdelwahid; Sierro, Francisco J.; Krijgsman, Wout

2017-07-01

Tectonic processes in the Gibraltar region are associated with Africa-Iberia convergence and the formation of the Betic-Rif orogenic system. The Late Miocene shortening recorded in the Rif orogen resulted in gradual shallowing and eventual closure of the Rifian Corridor, a narrow marine gateway connecting the Atlantic Ocean with the Mediterranean Sea. This closure is associated with paleoenvironmental changes that ultimately led to the Mediterranean Messinian Salinity Crisis. Here we present a structural analysis based on a combination of field kinematic data and interpretation of reflection seismic lines acquired for petroleum exploration to understand the deformational phases associated with the closure of the Rifian Corridor. We show the succession of three Late Miocene to present day events, an initial thin-skinned nappe thrusting, followed by regional subsidence and continued by thick-skinned contraction. The transition from in sequence thin-skinned tectonics during subduction to thick-skinned contraction during continental collision resulted in significant acceleration of tectonic uplift and associated exhumation. This is related to a change in the regional deformation linked to plate convergence, but possibly also coupled with deep lithospheric or dynamic topography processes. Such a mechanism is also common for other Mediterranean orogens during late stages of slab retreat, where accelerated tectonics resulted in rapid sedimentation and associated basins evolution. We conclude that the thick-skinned contraction in the Rif orogeny initiated in the late Tortonian, has created a cumulative uplift in the order of 1 km, and provided high enough uplift rates to close the Rifian Corridor.
Tectonic sequence stratigraphy, Early Permian Dry Mountain trough, east-central Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snyder, W.S.; Gallegos, D.M.; Spinosa, C.

1991-06-01

The Early Permian Dry Mountain trough (DMT) of east-central Nevada is one of several tectonic basins and associated uplifts that developed along the continenetal margin during the latest Pennsylvanian-Early Permian Dry Mountain tectonic phase. The sequence stratigraphy reflects a combination of eustatic sea level changes and tectonic uplift or subsidence. Fewer than one to only a few million years separate the development of sequence boundaries within the DMT. At this scale, differences among published eustasy curves preclude their use as definitive tools to identify eustatically controlled sequence boundaries. Nevertheless, available data indicate several pulses of tectonism affected sedimentation within themore » DMT. The authors are attempting to develop criteria to distinguish tectonic from eustatic sequence boundaries. Detailed biostratigraphic data are required to provide an independent check on the correlation of sequence boundaries between measured sections. For example, the same age boundary may reflect tectonic uplift in one part of the basin and subsidence in another. The uplift may or may not result in subaerial exposure and erosion. For those boundaries that do not result from subaerial exposure, lithofacies and biofacies analyses are required to infer relative uplift (water depth decrease) or subsidence (water depth increase). There are inherent resolution limitations in both the paleontologic and sedimentologic methodologies. These limitations, combined with those of eustasy curves, dictate the preliminary nature of their results.« less
The Tethys Sea and the Alpine-Himalayan orogenic belt; mega-elements in a new global tectonic system

NASA Astrophysics Data System (ADS)

Storetvedt, K. M.

Analysis of Meso-Cainozoic palaeomagnetic data for Africa, India and Eurasia has led to the development of a new mobilistic Alpine plate tectonic model characterized by a hierarchical system of plates in relative rotation. The new model, which discounts seafloor spreading, implies that there have been no significant palaeogeographic changes in the overall distribution of continental and oceanic regions. The mid-oceanic ridges are interpreted as transpressive tectonic features caused by rotation of megaplates (containing both continental and oceanic crust), the isostatic uplift due to crustal/lithospheric thickening giving rise to the general ridge topography as well as to the ridge-parallel structural grain. The new plate tectonic theory gains strong support from a variety of geophysical, geological and palaeoclimatological evidence, and several observations that have remained enigmatic or awkward within the context of the orthodox model can be readily accounted for in the new tectonic framework. The model maintains the Tethys as a relatively narrow epicontinental sea which, during its maximum extent, stretched latitudinally from the Caribbean, across the Central Atlantic to SE Asia. The Alpine-Himalayan orogenic belt developed along the boundary of two megaplates in relative rotation, which provided a transpressive tectonic regime. The location of the plate boundary to the north of the Mediterranean has important implications for discussion of Mediterranean microplates. For example, it now seems that Italy has been subjected to 10-15° of clockwise microplate rotation; previous conclusions in favour of 30-40° of anticlockwise rotation are regarded as artefacts which arise from incorrectly linking the Mediterranean region to the European palaeomagnetic frame instead of to the African one. The model suggests further that the Indo-Pakistani plate was closely tied to Eurasia; this challenges the conventional view that the Peninsula was part of an alleged Gondwanaland
Global tectonic of Enceladus driven by subsidence of South Polar Terrain

NASA Astrophysics Data System (ADS)

Czechowski, Leszek

2016-07-01

Enceladus is the smallest celestial body in the Solar System where volcanic and tectonic activities are observed. Every second, the mass of ~200 kg is ejected into space from the South Polar Terrain (SPT) - [1]. Our hypothesis states that this mass loss is the main driving mechanism of the tectonic processes. The hypothesis is presented in [2] and [3]. We find that the loss of the volatiles results in a void, an instability, and motion of solid matter to fill the void. The motion includes: (i) Subsidence of the 'lithosphere' of SPT. (ii) Flow of the matter in the mantle. (iii) Motion of plates adjacent to SPT towards the active region. The numerical model of the subsidence process is developed. It is based on the model of thermal convection in the mantle. Special boundary conditions are applied that could simulate subsidence of SPT. If emerging void is being filled by the subsidence of SPT only, then the velocity of subsidence is ~0.05 mm per yr. However, numerical calculations indicate that all three types of motion are usually important. The role of a given motion depends on the viscosity distribution. Generally, for most of the models the subsidence is ~0.02 mm per yr, but mantle flow and plates' motion also play a role in filling the void. The preliminary results of the numerical model indicate also that the velocity of adjacent plates could be ~0.02 mm per yr for the Newtonian rheology. The SPT is not compressed, so "tiger stripes" could exist for long time. Only after significant subsidence the regime of stresses changes to compression. It means the end of activity in a given region. The future region of activity is suggested. Acknowledgments This work was partially supported by the National Science Centre (grant 2011/01/B/ST10/06653). Computer resources of Interdisciplinary Centre for Mathematical and Computational Modeling of University of Warsaw were also used in the research References [1] Spencer, J. R., et al. (2009) Enceladus: An Active Cryovolcanic
Tectonic granulation of terrestrial planets in connection with their orbital frequencies

NASA Astrophysics Data System (ADS)

Kochemasov, G.

2007-08-01

The comparative wave planetology states that "orbits make structures" [1, 2 & others]. Moving in elliptical keplerian orbits with periodically changing accelerations celestial bodies are subjected to a warping action of inertia-gravity waves. In rotating bodies they acquire a stationary character and go in 4 crossing ortho- and diagonal directions. Interference of these directions produces uplifting (+), subsiding (-) and neutral (0) tectonic blocks size of which depends on lengths of warping waves. The fundamental wave 1 long 2πR produces ubiquitous tectonic dichotomy - an opposition of two segments - one (+), another (-). Well known at Earth, Mars and the Moon it is not so sharp at Venus and just discovered on Mercury (Dr. Ksanfomality's telescopic observations of a huge basin > 2000 km in diameter on unknown portion of Mercury's surface). Asteroids at the farthest end of the terrestrial planets row all show oblong and convexo-concave shape due to warping action of wave 1. The fundamental wave 1 has overtones of which the first long πR produces tectonic sectors - very prominent features. At Earth, for an example, these are continents and secondary oceans (the primary Pacific is a segment - a part of the dichotomous structure). On these common for all planets basic warpings are superimposed individual warpings or tectonic granules. Their sizes are inversely proportional to orbital frequencies: higher frequency - smaller grain and, vice versa, lower frequency - larger grain. Starting from the solar photosphere (it orbits the center of the solar system with frequency 1/1month) one has the following row of tectonic grains sizes (a half of a wavelength): photosphere πR/60, Mercury πR/16, Venus πR/6, Earth πR/4, Mars πR/2, asteroids πR/1. Photosphere grains are famous solar supergranules about 30000 km across (this size was never explained by the solar physics). Mercury's grains are typical small basins occupying 3-4° of a big circle arc. Venus' grains are 12

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